From 793b18a4b500ad497136380c893960eae159fbc0 Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Mon, 27 Jul 2026 14:30:04 -0700
Subject: [PATCH 01/13] test: Fix imports

---
 packages/blockly/package.json                    |  4 ++++
 packages/blockly/tests/mocha/aria_test.js        |  4 ++--
 packages/blockly/tests/mocha/block_json_test.js  |  4 ++--
 packages/blockly/tests/mocha/block_test.js       | 16 ++++++++--------
 .../blockly/tests/mocha/blocks/lists_test.js     |  4 ++--
 .../tests/mocha/blocks/logic_ternary_test.js     |  4 ++--
 .../blockly/tests/mocha/blocks/loops_test.js     |  4 ++--
 .../tests/mocha/blocks/procedures_test.js        |  4 ++--
 .../blockly/tests/mocha/blocks/variables_test.js |  4 ++--
 packages/blockly/tests/mocha/clipboard_test.js   |  2 +-
 .../tests/mocha/comment_deserialization_test.js  |  2 +-
 packages/blockly/tests/mocha/comment_test.js     |  4 ++--
 .../blockly/tests/mocha/comment_view_test.js     |  2 +-
 .../tests/mocha/connection_checker_test.js       |  4 ++--
 .../blockly/tests/mocha/connection_db_test.js    |  6 +++---
 packages/blockly/tests/mocha/connection_test.js  |  2 +-
 .../tests/mocha/contextmenu_items_test.js        |  2 +-
 packages/blockly/tests/mocha/contextmenu_test.js |  6 +++---
 packages/blockly/tests/mocha/dialog_test.js      |  2 +-
 packages/blockly/tests/mocha/dropdowndiv_test.js |  9 ++++++---
 .../tests/mocha/event_block_change_test.js       |  2 +-
 .../tests/mocha/event_block_create_test.js       |  4 ++--
 .../tests/mocha/event_block_delete_test.js       |  2 +-
 .../blockly/tests/mocha/event_block_drag_test.js |  2 +-
 ...event_block_field_intermediate_change_test.js |  2 +-
 .../blockly/tests/mocha/event_block_move_test.js |  2 +-
 .../tests/mocha/event_bubble_open_test.js        |  2 +-
 packages/blockly/tests/mocha/event_click_test.js |  2 +-
 .../tests/mocha/event_comment_change_test.js     |  2 +-
 .../tests/mocha/event_comment_collapse_test.js   |  2 +-
 .../tests/mocha/event_comment_create_test.js     |  2 +-
 .../tests/mocha/event_comment_delete_test.js     |  2 +-
 .../tests/mocha/event_comment_drag_test.js       |  2 +-
 .../tests/mocha/event_comment_move_test.js       |  2 +-
 .../tests/mocha/event_comment_resize_test.js     |  2 +-
 .../blockly/tests/mocha/event_selected_test.js   |  2 +-
 packages/blockly/tests/mocha/event_test.js       |  6 +++---
 .../tests/mocha/event_theme_change_test.js       |  2 +-
 .../mocha/event_toolbox_item_select_test.js      |  2 +-
 .../tests/mocha/event_trashcan_open_test.js      |  2 +-
 .../blockly/tests/mocha/event_var_create_test.js |  2 +-
 .../blockly/tests/mocha/event_var_delete_test.js |  2 +-
 .../blockly/tests/mocha/event_var_rename_test.js |  2 +-
 .../tests/mocha/event_var_type_change_test.js    |  2 +-
 .../blockly/tests/mocha/event_viewport_test.js   |  2 +-
 packages/blockly/tests/mocha/extensions_test.js  |  2 +-
 .../blockly/tests/mocha/field_checkbox_test.js   |  4 ++--
 .../blockly/tests/mocha/field_dropdown_test.js   |  4 ++--
 packages/blockly/tests/mocha/field_image_test.js |  4 ++--
 .../tests/mocha/field_label_serializable_test.js |  4 ++--
 packages/blockly/tests/mocha/field_label_test.js |  4 ++--
 .../blockly/tests/mocha/field_number_test.js     |  4 ++--
 .../blockly/tests/mocha/field_registry_test.js   |  4 ++--
 packages/blockly/tests/mocha/field_test.js       |  4 ++--
 .../blockly/tests/mocha/field_textinput_test.js  |  4 ++--
 .../blockly/tests/mocha/field_variable_test.js   |  4 ++--
 packages/blockly/tests/mocha/flyout_test.js      |  2 +-
 .../blockly/tests/mocha/focus_manager_test.js    |  7 ++-----
 .../tests/mocha/focusable_tree_traverser_test.js |  6 +++---
 packages/blockly/tests/mocha/generator_test.js   | 14 +++++++-------
 packages/blockly/tests/mocha/gesture_test.js     |  4 ++--
 packages/blockly/tests/mocha/icon_test.js        |  4 ++--
 packages/blockly/tests/mocha/index.html          | 16 +++++++++++++++-
 packages/blockly/tests/mocha/input_test.js       |  2 +-
 .../blockly/tests/mocha/insertion_marker_test.js |  2 +-
 .../tests/mocha/jso_deserialization_test.js      |  4 ++--
 .../tests/mocha/jso_serialization_test.js        |  4 ++--
 packages/blockly/tests/mocha/json_test.js        |  2 +-
 .../tests/mocha/keyboard_movement_test.js        |  4 ++--
 .../mocha/keyboard_navigation_controller_test.js |  2 +-
 .../tests/mocha/keyboard_navigation_test.js      |  4 ++--
 packages/blockly/tests/mocha/layering_test.js    |  2 +-
 packages/blockly/tests/mocha/menu_item_test.js   |  2 +-
 packages/blockly/tests/mocha/metrics_test.js     |  2 +-
 packages/blockly/tests/mocha/mutator_test.js     |  2 +-
 packages/blockly/tests/mocha/names_test.js       |  2 +-
 packages/blockly/tests/mocha/navigation_test.js  |  2 +-
 .../tests/mocha/old_workspace_comment_test.js    |  2 +-
 .../blockly/tests/mocha/procedure_map_test.js    |  2 +-
 packages/blockly/tests/mocha/rect_test.js        |  2 +-
 packages/blockly/tests/mocha/registry_test.js    |  2 +-
 .../tests/mocha/render_management_test.js        |  2 +-
 packages/blockly/tests/mocha/serializer_test.js  |  4 ++--
 .../blockly/tests/mocha/shortcut_items_test.js   |  4 ++--
 .../tests/mocha/shortcut_registry_test.js        |  2 +-
 .../tests/mocha/test_helpers/code_generation.js  |  2 +-
 .../blockly/tests/mocha/test_helpers/events.js   |  2 +-
 .../blockly/tests/mocha/test_helpers/fields.js   |  2 +-
 .../tests/mocha/test_helpers/icon_mocks.js       |  8 ++++----
 .../tests/mocha/test_helpers/p5_blocks.js        |  2 +-
 .../tests/mocha/test_helpers/procedures.js       |  6 +++---
 .../tests/mocha/test_helpers/serialization.js    |  2 +-
 .../tests/mocha/test_helpers/setup_teardown.js   |  4 ++--
 .../tests/mocha/test_helpers/user_input.js       |  2 +-
 .../tests/mocha/test_helpers/variables.js        |  2 +-
 .../blockly/tests/mocha/test_helpers/warnings.js |  2 +-
 .../tests/mocha/test_helpers/workspace.js        |  4 ++--
 packages/blockly/tests/mocha/theme_test.js       |  4 ++--
 packages/blockly/tests/mocha/toast_test.js       |  2 +-
 packages/blockly/tests/mocha/toolbox_test.js     |  2 +-
 packages/blockly/tests/mocha/tooltip_test.js     |  2 +-
 packages/blockly/tests/mocha/touch_test.js       |  2 +-
 packages/blockly/tests/mocha/trashcan_test.js    |  6 +++---
 packages/blockly/tests/mocha/utils_test.js       |  2 +-
 .../blockly/tests/mocha/variable_map_test.js     |  2 +-
 .../blockly/tests/mocha/variable_model_test.js   |  2 +-
 packages/blockly/tests/mocha/widget_div_test.js  |  2 +-
 .../tests/mocha/workspace_comment_test.js        |  2 +-
 .../blockly/tests/mocha/workspace_svg_test.js    |  4 ++--
 packages/blockly/tests/mocha/xml_test.js         |  2 +-
 .../blockly/tests/mocha/zoom_controls_test.js    |  4 ++--
 111 files changed, 195 insertions(+), 177 deletions(-)

diff --git a/packages/blockly/package.json b/packages/blockly/package.json
index 7018ad0bd21..71770f31bad 100644
--- a/packages/blockly/package.json
+++ b/packages/blockly/package.json
@@ -19,6 +19,10 @@
   "browser": {
     "jsdom": false
   },
+  "imports": {
+    "#core/*": "./build/src/core/*",
+    "#generators/*": "./build/src/generators/*"
+  },
   "scripts": {
     "build": "gulp build",
     "build-debug": "gulp build --verbose --debug",
diff --git a/packages/blockly/tests/mocha/aria_test.js b/packages/blockly/tests/mocha/aria_test.js
index 20bb35aa5c6..b68954a06da 100644
--- a/packages/blockly/tests/mocha/aria_test.js
+++ b/packages/blockly/tests/mocha/aria_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {getInputLabelsSubset} from '../../build/src/core/block_aria_composer.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {getInputLabelsSubset} from '#core/block_aria_composer.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/block_json_test.js b/packages/blockly/tests/mocha/block_json_test.js
index 02ed05a012d..507738ecc9a 100644
--- a/packages/blockly/tests/mocha/block_json_test.js
+++ b/packages/blockly/tests/mocha/block_json_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {Align} from '../../build/src/core/inputs/align.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {Align} from '#core/inputs/align.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/block_test.js b/packages/blockly/tests/mocha/block_test.js
index 9762f466ce5..d7c4dd99bda 100644
--- a/packages/blockly/tests/mocha/block_test.js
+++ b/packages/blockly/tests/mocha/block_test.js
@@ -4,14 +4,14 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {ConnectionType} from '../../build/src/core/connection_type.js';
-import {EventType} from '../../build/src/core/events/type.js';
-import * as eventUtils from '../../build/src/core/events/utils.js';
-import {IconType} from '../../build/src/core/icons/icon_types.js';
-import {EndRowInput} from '../../build/src/core/inputs/end_row_input.js';
-import {isCommentIcon} from '../../build/src/core/interfaces/i_comment_icon.js';
-import {Size} from '../../build/src/core/utils/size.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {ConnectionType} from '#core/connection_type.js';
+import {EventType} from '#core/events/type.js';
+import * as eventUtils from '#core/events/utils.js';
+import {IconType} from '#core/icons/icon_types.js';
+import {EndRowInput} from '#core/inputs/end_row_input.js';
+import {isCommentIcon} from '#core/interfaces/i_comment_icon.js';
+import {Size} from '#core/utils/size.js';
+import {assert} from 'chai';
 import {createRenderedBlock} from './test_helpers/block_definitions.js';
 import {
   createChangeListenerSpy,
diff --git a/packages/blockly/tests/mocha/blocks/lists_test.js b/packages/blockly/tests/mocha/blocks/lists_test.js
index e749fae90a7..9fafbb54788 100644
--- a/packages/blockly/tests/mocha/blocks/lists_test.js
+++ b/packages/blockly/tests/mocha/blocks/lists_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {ConnectionType} from '../../../build/src/core/connection_type.js';
-import {assert} from '../../../node_modules/chai/index.js';
+import {ConnectionType} from '#core/connection_type.js';
+import {assert} from 'chai';
 import {defineStatementBlock} from '../test_helpers/block_definitions.js';
 import {runSerializationTestSuite} from '../test_helpers/serialization.js';
 import {
diff --git a/packages/blockly/tests/mocha/blocks/logic_ternary_test.js b/packages/blockly/tests/mocha/blocks/logic_ternary_test.js
index 3d343a7caec..fd0998cafe8 100644
--- a/packages/blockly/tests/mocha/blocks/logic_ternary_test.js
+++ b/packages/blockly/tests/mocha/blocks/logic_ternary_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as eventUtils from '../../../build/src/core/events/utils.js';
-import {assert} from '../../../node_modules/chai/index.js';
+import * as eventUtils from '#core/events/utils.js';
+import {assert} from 'chai';
 import {runSerializationTestSuite} from '../test_helpers/serialization.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/blocks/loops_test.js b/packages/blockly/tests/mocha/blocks/loops_test.js
index eb040c884a7..ebc0ad0bc6a 100644
--- a/packages/blockly/tests/mocha/blocks/loops_test.js
+++ b/packages/blockly/tests/mocha/blocks/loops_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../../build/src/core/blockly.js';
-import {assert} from '../../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/blocks/procedures_test.js b/packages/blockly/tests/mocha/blocks/procedures_test.js
index 8e226186bbe..87ce1478134 100644
--- a/packages/blockly/tests/mocha/blocks/procedures_test.js
+++ b/packages/blockly/tests/mocha/blocks/procedures_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../../build/src/core/blockly.js';
-import {assert} from '../../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {defineRowBlock} from '../test_helpers/block_definitions.js';
 import {
   assertCallBlockStructure,
diff --git a/packages/blockly/tests/mocha/blocks/variables_test.js b/packages/blockly/tests/mocha/blocks/variables_test.js
index 724e2e543d0..0b440d9a19f 100644
--- a/packages/blockly/tests/mocha/blocks/variables_test.js
+++ b/packages/blockly/tests/mocha/blocks/variables_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {nameUsedWithConflictingParam} from '../../../build/src/core/variables.js';
-import {assert} from '../../../node_modules/chai/index.js';
+import {nameUsedWithConflictingParam} from '#core/variables.js';
+import {assert} from 'chai';
 import {
   MockParameterModelWithVar,
   MockProcedureModel,
diff --git a/packages/blockly/tests/mocha/clipboard_test.js b/packages/blockly/tests/mocha/clipboard_test.js
index ff49c0e303c..cbba541fc19 100644
--- a/packages/blockly/tests/mocha/clipboard_test.js
+++ b/packages/blockly/tests/mocha/clipboard_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   assertEventFired,
   createChangeListenerSpy,
diff --git a/packages/blockly/tests/mocha/comment_deserialization_test.js b/packages/blockly/tests/mocha/comment_deserialization_test.js
index 8299b8215d2..e4a1dc6dae9 100644
--- a/packages/blockly/tests/mocha/comment_deserialization_test.js
+++ b/packages/blockly/tests/mocha/comment_deserialization_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/comment_test.js b/packages/blockly/tests/mocha/comment_test.js
index eb0f6ab9d75..feab6bda14f 100644
--- a/packages/blockly/tests/mocha/comment_test.js
+++ b/packages/blockly/tests/mocha/comment_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {EventType} from '../../build/src/core/events/type.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {EventType} from '#core/events/type.js';
+import {assert} from 'chai';
 import {assertEventFired} from './test_helpers/events.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/comment_view_test.js b/packages/blockly/tests/mocha/comment_view_test.js
index a60a7a973ff..068649c77f1 100644
--- a/packages/blockly/tests/mocha/comment_view_test.js
+++ b/packages/blockly/tests/mocha/comment_view_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/connection_checker_test.js b/packages/blockly/tests/mocha/connection_checker_test.js
index bdbcb70a6ec..3c50dd03d76 100644
--- a/packages/blockly/tests/mocha/connection_checker_test.js
+++ b/packages/blockly/tests/mocha/connection_checker_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {ConnectionType} from '../../build/src/core/connection_type.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {ConnectionType} from '#core/connection_type.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/connection_db_test.js b/packages/blockly/tests/mocha/connection_db_test.js
index 459c59e3ab4..7b8afd2118d 100644
--- a/packages/blockly/tests/mocha/connection_db_test.js
+++ b/packages/blockly/tests/mocha/connection_db_test.js
@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {ConnectionType} from '../../build/src/core/connection_type.js';
-import * as idGenerator from '../../build/src/core/utils/idgenerator.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {ConnectionType} from '#core/connection_type.js';
+import * as idGenerator from '#core/utils/idgenerator.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/connection_test.js b/packages/blockly/tests/mocha/connection_test.js
index b36f358eac3..5931d87ef42 100644
--- a/packages/blockly/tests/mocha/connection_test.js
+++ b/packages/blockly/tests/mocha/connection_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   defineRowBlock,
   defineStackBlock,
diff --git a/packages/blockly/tests/mocha/contextmenu_items_test.js b/packages/blockly/tests/mocha/contextmenu_items_test.js
index 3316d626b0a..8021252f9a5 100644
--- a/packages/blockly/tests/mocha/contextmenu_items_test.js
+++ b/packages/blockly/tests/mocha/contextmenu_items_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/contextmenu_test.js b/packages/blockly/tests/mocha/contextmenu_test.js
index 8cd71172766..3aa2ce5fcca 100644
--- a/packages/blockly/tests/mocha/contextmenu_test.js
+++ b/packages/blockly/tests/mocha/contextmenu_test.js
@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {callbackFactory} from '../../build/src/core/contextmenu.js';
-import * as xmlUtils from '../../build/src/core/utils/xml.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {callbackFactory} from '#core/contextmenu.js';
+import * as xmlUtils from '#core/utils/xml.js';
+import {assert} from 'chai';
 import {
   defineRowBlock,
   defineStackBlock,
diff --git a/packages/blockly/tests/mocha/dialog_test.js b/packages/blockly/tests/mocha/dialog_test.js
index ef8e17cf714..7ade12362ce 100644
--- a/packages/blockly/tests/mocha/dialog_test.js
+++ b/packages/blockly/tests/mocha/dialog_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/dropdowndiv_test.js b/packages/blockly/tests/mocha/dropdowndiv_test.js
index 62e8c3dc923..bc9df1a23b5 100644
--- a/packages/blockly/tests/mocha/dropdowndiv_test.js
+++ b/packages/blockly/tests/mocha/dropdowndiv_test.js
@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {Rect} from '../../build/src/core/utils/rect.js';
-import * as style from '../../build/src/core/utils/style.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {Rect} from '#core/utils/rect.js';
+import * as style from '#core/utils/style.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
@@ -196,6 +196,9 @@ suite('DropDownDiv', function () {
     });
 
     test('sets the dropdowndiv as owned by the workspace', function () {
+      // Set the bounds element explicitly rather than relying on a previous
+      // test having set this module-global, so this test is order-independent.
+      Blockly.DropDownDiv.setBoundsElement(document.body);
       const block = this.setUpBlockWithField();
       const field = Array.from(block.getFields())[0];
 
diff --git a/packages/blockly/tests/mocha/event_block_change_test.js b/packages/blockly/tests/mocha/event_block_change_test.js
index 9e1f9c3103e..de459a9c039 100644
--- a/packages/blockly/tests/mocha/event_block_change_test.js
+++ b/packages/blockly/tests/mocha/event_block_change_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {defineMutatorBlocks} from './test_helpers/block_definitions.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/event_block_create_test.js b/packages/blockly/tests/mocha/event_block_create_test.js
index b0f5001de33..2cdbcba232a 100644
--- a/packages/blockly/tests/mocha/event_block_create_test.js
+++ b/packages/blockly/tests/mocha/event_block_create_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {EventType} from '../../build/src/core/events/type.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {EventType} from '#core/events/type.js';
+import {assert} from 'chai';
 import {defineRowBlock} from './test_helpers/block_definitions.js';
 import {assertEventFired} from './test_helpers/events.js';
 import {
diff --git a/packages/blockly/tests/mocha/event_block_delete_test.js b/packages/blockly/tests/mocha/event_block_delete_test.js
index e2fb5b8ce88..f423a4064bb 100644
--- a/packages/blockly/tests/mocha/event_block_delete_test.js
+++ b/packages/blockly/tests/mocha/event_block_delete_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {defineRowBlock} from './test_helpers/block_definitions.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/event_block_drag_test.js b/packages/blockly/tests/mocha/event_block_drag_test.js
index cc71e3bf084..c4859ddc086 100644
--- a/packages/blockly/tests/mocha/event_block_drag_test.js
+++ b/packages/blockly/tests/mocha/event_block_drag_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {defineRowBlock} from './test_helpers/block_definitions.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/event_block_field_intermediate_change_test.js b/packages/blockly/tests/mocha/event_block_field_intermediate_change_test.js
index d917dadcdd5..7a4c23bd575 100644
--- a/packages/blockly/tests/mocha/event_block_field_intermediate_change_test.js
+++ b/packages/blockly/tests/mocha/event_block_field_intermediate_change_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_block_move_test.js b/packages/blockly/tests/mocha/event_block_move_test.js
index 6d1890eebeb..c29d9a6ae8d 100644
--- a/packages/blockly/tests/mocha/event_block_move_test.js
+++ b/packages/blockly/tests/mocha/event_block_move_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {defineRowBlock} from './test_helpers/block_definitions.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/event_bubble_open_test.js b/packages/blockly/tests/mocha/event_bubble_open_test.js
index a445a6a7819..12ccd774b29 100644
--- a/packages/blockly/tests/mocha/event_bubble_open_test.js
+++ b/packages/blockly/tests/mocha/event_bubble_open_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {defineMutatorBlocks} from './test_helpers/block_definitions.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/event_click_test.js b/packages/blockly/tests/mocha/event_click_test.js
index 5c4afbcadf9..00d3feb2fcf 100644
--- a/packages/blockly/tests/mocha/event_click_test.js
+++ b/packages/blockly/tests/mocha/event_click_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {defineRowBlock} from './test_helpers/block_definitions.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/event_comment_change_test.js b/packages/blockly/tests/mocha/event_comment_change_test.js
index edb539ef555..e25b008b93c 100644
--- a/packages/blockly/tests/mocha/event_comment_change_test.js
+++ b/packages/blockly/tests/mocha/event_comment_change_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_comment_collapse_test.js b/packages/blockly/tests/mocha/event_comment_collapse_test.js
index 5c3f61054a1..d7cd95aa071 100644
--- a/packages/blockly/tests/mocha/event_comment_collapse_test.js
+++ b/packages/blockly/tests/mocha/event_comment_collapse_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_comment_create_test.js b/packages/blockly/tests/mocha/event_comment_create_test.js
index 71ef8ed1b75..1ba9bd2ea69 100644
--- a/packages/blockly/tests/mocha/event_comment_create_test.js
+++ b/packages/blockly/tests/mocha/event_comment_create_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_comment_delete_test.js b/packages/blockly/tests/mocha/event_comment_delete_test.js
index dd9f0dd2286..7b880c34ee0 100644
--- a/packages/blockly/tests/mocha/event_comment_delete_test.js
+++ b/packages/blockly/tests/mocha/event_comment_delete_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_comment_drag_test.js b/packages/blockly/tests/mocha/event_comment_drag_test.js
index f6685cc5bdf..2e9c385a460 100644
--- a/packages/blockly/tests/mocha/event_comment_drag_test.js
+++ b/packages/blockly/tests/mocha/event_comment_drag_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_comment_move_test.js b/packages/blockly/tests/mocha/event_comment_move_test.js
index b3acea990a6..68e28f91d32 100644
--- a/packages/blockly/tests/mocha/event_comment_move_test.js
+++ b/packages/blockly/tests/mocha/event_comment_move_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_comment_resize_test.js b/packages/blockly/tests/mocha/event_comment_resize_test.js
index bed3e733a65..7b092497ab7 100644
--- a/packages/blockly/tests/mocha/event_comment_resize_test.js
+++ b/packages/blockly/tests/mocha/event_comment_resize_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_selected_test.js b/packages/blockly/tests/mocha/event_selected_test.js
index d5fefea0d75..b0c4d1d4130 100644
--- a/packages/blockly/tests/mocha/event_selected_test.js
+++ b/packages/blockly/tests/mocha/event_selected_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {defineRowBlock} from './test_helpers/block_definitions.js';
 import {createChangeListenerSpy} from './test_helpers/events.js';
 import {
diff --git a/packages/blockly/tests/mocha/event_test.js b/packages/blockly/tests/mocha/event_test.js
index 0bd9dd6b961..eb43b099deb 100644
--- a/packages/blockly/tests/mocha/event_test.js
+++ b/packages/blockly/tests/mocha/event_test.js
@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import * as eventUtils from '../../build/src/core/events/utils.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import * as eventUtils from '#core/events/utils.js';
+import {assert} from 'chai';
 import {
   assertEventEquals,
   assertNthCallEventArgEquals,
diff --git a/packages/blockly/tests/mocha/event_theme_change_test.js b/packages/blockly/tests/mocha/event_theme_change_test.js
index 396347c9e13..f514599d131 100644
--- a/packages/blockly/tests/mocha/event_theme_change_test.js
+++ b/packages/blockly/tests/mocha/event_theme_change_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_toolbox_item_select_test.js b/packages/blockly/tests/mocha/event_toolbox_item_select_test.js
index 02484c35bc1..5bbb879e304 100644
--- a/packages/blockly/tests/mocha/event_toolbox_item_select_test.js
+++ b/packages/blockly/tests/mocha/event_toolbox_item_select_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_trashcan_open_test.js b/packages/blockly/tests/mocha/event_trashcan_open_test.js
index 47da09a075a..80869b4d50d 100644
--- a/packages/blockly/tests/mocha/event_trashcan_open_test.js
+++ b/packages/blockly/tests/mocha/event_trashcan_open_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_var_create_test.js b/packages/blockly/tests/mocha/event_var_create_test.js
index 79af41281de..730c5fcd236 100644
--- a/packages/blockly/tests/mocha/event_var_create_test.js
+++ b/packages/blockly/tests/mocha/event_var_create_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_var_delete_test.js b/packages/blockly/tests/mocha/event_var_delete_test.js
index 93d9ef0ba2d..098b5a6a43c 100644
--- a/packages/blockly/tests/mocha/event_var_delete_test.js
+++ b/packages/blockly/tests/mocha/event_var_delete_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_var_rename_test.js b/packages/blockly/tests/mocha/event_var_rename_test.js
index b6d77cb35bd..1edefe3a4f3 100644
--- a/packages/blockly/tests/mocha/event_var_rename_test.js
+++ b/packages/blockly/tests/mocha/event_var_rename_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_var_type_change_test.js b/packages/blockly/tests/mocha/event_var_type_change_test.js
index 066c145a3ef..3a7cd890c47 100644
--- a/packages/blockly/tests/mocha/event_var_type_change_test.js
+++ b/packages/blockly/tests/mocha/event_var_type_change_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/event_viewport_test.js b/packages/blockly/tests/mocha/event_viewport_test.js
index cd11079fa32..fbf0c780e36 100644
--- a/packages/blockly/tests/mocha/event_viewport_test.js
+++ b/packages/blockly/tests/mocha/event_viewport_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/extensions_test.js b/packages/blockly/tests/mocha/extensions_test.js
index 8c41861d5d8..515d70378c3 100644
--- a/packages/blockly/tests/mocha/extensions_test.js
+++ b/packages/blockly/tests/mocha/extensions_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/field_checkbox_test.js b/packages/blockly/tests/mocha/field_checkbox_test.js
index 2c5a249e992..e432ecd73f4 100644
--- a/packages/blockly/tests/mocha/field_checkbox_test.js
+++ b/packages/blockly/tests/mocha/field_checkbox_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {defineRowBlock} from './test_helpers/block_definitions.js';
 import {
   assertFieldValue,
diff --git a/packages/blockly/tests/mocha/field_dropdown_test.js b/packages/blockly/tests/mocha/field_dropdown_test.js
index e08b2202f60..20f77c7e69a 100644
--- a/packages/blockly/tests/mocha/field_dropdown_test.js
+++ b/packages/blockly/tests/mocha/field_dropdown_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   createTestBlock,
   defineRowBlock,
diff --git a/packages/blockly/tests/mocha/field_image_test.js b/packages/blockly/tests/mocha/field_image_test.js
index 36607f9e0b5..83d867a9e15 100644
--- a/packages/blockly/tests/mocha/field_image_test.js
+++ b/packages/blockly/tests/mocha/field_image_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   assertFieldValue,
   runConstructorSuiteTests,
diff --git a/packages/blockly/tests/mocha/field_label_serializable_test.js b/packages/blockly/tests/mocha/field_label_serializable_test.js
index 443cc6d1753..3cb6a622be4 100644
--- a/packages/blockly/tests/mocha/field_label_serializable_test.js
+++ b/packages/blockly/tests/mocha/field_label_serializable_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   createTestBlock,
   defineRowBlock,
diff --git a/packages/blockly/tests/mocha/field_label_test.js b/packages/blockly/tests/mocha/field_label_test.js
index 6e5cd15226d..586efeb857e 100644
--- a/packages/blockly/tests/mocha/field_label_test.js
+++ b/packages/blockly/tests/mocha/field_label_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {createTestBlock} from './test_helpers/block_definitions.js';
 import {
   assertFieldValue,
diff --git a/packages/blockly/tests/mocha/field_number_test.js b/packages/blockly/tests/mocha/field_number_test.js
index b950f2b0329..3f21f93612e 100644
--- a/packages/blockly/tests/mocha/field_number_test.js
+++ b/packages/blockly/tests/mocha/field_number_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {defineRowBlock} from './test_helpers/block_definitions.js';
 import {runTestCases} from './test_helpers/common.js';
 import {
diff --git a/packages/blockly/tests/mocha/field_registry_test.js b/packages/blockly/tests/mocha/field_registry_test.js
index 1f19477dee1..956a300df0e 100644
--- a/packages/blockly/tests/mocha/field_registry_test.js
+++ b/packages/blockly/tests/mocha/field_registry_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/field_test.js b/packages/blockly/tests/mocha/field_test.js
index adfc6b43c97..44a588fc636 100644
--- a/packages/blockly/tests/mocha/field_test.js
+++ b/packages/blockly/tests/mocha/field_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   addBlockTypeToCleanup,
   addMessageToCleanup,
diff --git a/packages/blockly/tests/mocha/field_textinput_test.js b/packages/blockly/tests/mocha/field_textinput_test.js
index a0faaeba7bc..2dd3a87df77 100644
--- a/packages/blockly/tests/mocha/field_textinput_test.js
+++ b/packages/blockly/tests/mocha/field_textinput_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   createTestBlock,
   defineRowBlock,
diff --git a/packages/blockly/tests/mocha/field_variable_test.js b/packages/blockly/tests/mocha/field_variable_test.js
index 06ca1f5b7e4..13f22edc2ed 100644
--- a/packages/blockly/tests/mocha/field_variable_test.js
+++ b/packages/blockly/tests/mocha/field_variable_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   createTestBlock,
   defineRowBlock,
diff --git a/packages/blockly/tests/mocha/flyout_test.js b/packages/blockly/tests/mocha/flyout_test.js
index e2812b25ba3..e0e50b1ceb8 100644
--- a/packages/blockly/tests/mocha/flyout_test.js
+++ b/packages/blockly/tests/mocha/flyout_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/focus_manager_test.js b/packages/blockly/tests/mocha/focus_manager_test.js
index 490fa4301b8..531a1506723 100644
--- a/packages/blockly/tests/mocha/focus_manager_test.js
+++ b/packages/blockly/tests/mocha/focus_manager_test.js
@@ -4,11 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {
-  FocusManager,
-  getFocusManager,
-} from '../../build/src/core/focus_manager.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {FocusManager, getFocusManager} from '#core/focus_manager.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/focusable_tree_traverser_test.js b/packages/blockly/tests/mocha/focusable_tree_traverser_test.js
index a384dd4be45..84e1bae5342 100644
--- a/packages/blockly/tests/mocha/focusable_tree_traverser_test.js
+++ b/packages/blockly/tests/mocha/focusable_tree_traverser_test.js
@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {FocusManager} from '../../build/src/core/focus_manager.js';
-import {FocusableTreeTraverser} from '../../build/src/core/utils/focusable_tree_traverser.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {FocusManager} from '#core/focus_manager.js';
+import {FocusableTreeTraverser} from '#core/utils/focusable_tree_traverser.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/generator_test.js b/packages/blockly/tests/mocha/generator_test.js
index 3c377e7c1ab..1fe42a43b90 100644
--- a/packages/blockly/tests/mocha/generator_test.js
+++ b/packages/blockly/tests/mocha/generator_test.js
@@ -4,13 +4,13 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {DartGenerator} from '../../build/src/generators/dart/dart_generator.js';
-import {JavascriptGenerator} from '../../build/src/generators/javascript/javascript_generator.js';
-import {LuaGenerator} from '../../build/src/generators/lua/lua_generator.js';
-import {PhpGenerator} from '../../build/src/generators/php/php_generator.js';
-import {PythonGenerator} from '../../build/src/generators/python/python_generator.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {DartGenerator} from '#generators/dart/dart_generator.js';
+import {JavascriptGenerator} from '#generators/javascript/javascript_generator.js';
+import {LuaGenerator} from '#generators/lua/lua_generator.js';
+import {PhpGenerator} from '#generators/php/php_generator.js';
+import {PythonGenerator} from '#generators/python/python_generator.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/gesture_test.js b/packages/blockly/tests/mocha/gesture_test.js
index 686f4f7aa09..648f5754caa 100644
--- a/packages/blockly/tests/mocha/gesture_test.js
+++ b/packages/blockly/tests/mocha/gesture_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {EventType} from '../../build/src/core/events/type.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {EventType} from '#core/events/type.js';
+import {assert} from 'chai';
 import {defineBasicBlockWithField} from './test_helpers/block_definitions.js';
 import {assertEventFired, assertEventNotFired} from './test_helpers/events.js';
 import {
diff --git a/packages/blockly/tests/mocha/icon_test.js b/packages/blockly/tests/mocha/icon_test.js
index c3e11879ce2..50a3645f05d 100644
--- a/packages/blockly/tests/mocha/icon_test.js
+++ b/packages/blockly/tests/mocha/icon_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {defineEmptyBlock} from './test_helpers/block_definitions.js';
 import {MockIcon, MockSerializableIcon} from './test_helpers/icon_mocks.js';
 import {
diff --git a/packages/blockly/tests/mocha/index.html b/packages/blockly/tests/mocha/index.html
index 53304cb63be..9e1bafec77d 100644
--- a/packages/blockly/tests/mocha/index.html
+++ b/packages/blockly/tests/mocha/index.html
@@ -5,6 +5,20 @@
     <title>Mocha Tests for Blockly</title>
 
     <link href="../../node_modules/mocha/mocha.css" rel="stylesheet" />
+
+    <!-- Resolve the bare/subpath specifiers used by the test modules so the
+         same import statements work in both the browser and under Node. The
+         "#core/" and "#generators/" prefixes mirror the "imports" field in
+         package.json (used by the Node runner). -->
+    <script type="importmap">
+      {
+        "imports": {
+          "chai": "../../node_modules/chai/index.js",
+          "#core/": "../../build/src/core/",
+          "#generators/": "../../build/src/generators/"
+        }
+      }
+    </script>
   </head>
   <style>
     #blocklyDiv {
@@ -273,7 +287,7 @@
       import * as Blockly from '../../build/blockly.loader.mjs';
       import '../../build/blocks.loader.mjs';
       import {javascriptGenerator} from '../../build/javascript.loader.mjs';
-      import {config} from '../../node_modules/chai/index.js';
+      import {config} from 'chai';
       config.showDiff = false;
 
       // Import tests.
diff --git a/packages/blockly/tests/mocha/input_test.js b/packages/blockly/tests/mocha/input_test.js
index b9f50484981..e27e6f7f3e4 100644
--- a/packages/blockly/tests/mocha/input_test.js
+++ b/packages/blockly/tests/mocha/input_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {createRenderedBlock} from './test_helpers/block_definitions.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/insertion_marker_test.js b/packages/blockly/tests/mocha/insertion_marker_test.js
index 8bcbb90dbe2..7af89a92999 100644
--- a/packages/blockly/tests/mocha/insertion_marker_test.js
+++ b/packages/blockly/tests/mocha/insertion_marker_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/jso_deserialization_test.js b/packages/blockly/tests/mocha/jso_deserialization_test.js
index f6b47d7de6a..9b8ab5d68cb 100644
--- a/packages/blockly/tests/mocha/jso_deserialization_test.js
+++ b/packages/blockly/tests/mocha/jso_deserialization_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {EventType} from '../../build/src/core/events/type.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {EventType} from '#core/events/type.js';
+import {assert} from 'chai';
 import {assertEventFired} from './test_helpers/events.js';
 import {
   MockParameterModel,
diff --git a/packages/blockly/tests/mocha/jso_serialization_test.js b/packages/blockly/tests/mocha/jso_serialization_test.js
index 15255545d98..0134ee6b53e 100644
--- a/packages/blockly/tests/mocha/jso_serialization_test.js
+++ b/packages/blockly/tests/mocha/jso_serialization_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   defineRowBlock,
   defineStackBlock,
diff --git a/packages/blockly/tests/mocha/json_test.js b/packages/blockly/tests/mocha/json_test.js
index 2e4b68df9ec..d1fccb6db96 100644
--- a/packages/blockly/tests/mocha/json_test.js
+++ b/packages/blockly/tests/mocha/json_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   addMessageToCleanup,
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/keyboard_movement_test.js b/packages/blockly/tests/mocha/keyboard_movement_test.js
index bb14e147cb8..029ae93f2a2 100644
--- a/packages/blockly/tests/mocha/keyboard_movement_test.js
+++ b/packages/blockly/tests/mocha/keyboard_movement_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   moveStatementTestBlocks,
   moveValueTestBlocks,
diff --git a/packages/blockly/tests/mocha/keyboard_navigation_controller_test.js b/packages/blockly/tests/mocha/keyboard_navigation_controller_test.js
index d2ba74b646d..a021db94057 100644
--- a/packages/blockly/tests/mocha/keyboard_navigation_controller_test.js
+++ b/packages/blockly/tests/mocha/keyboard_navigation_controller_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/keyboard_navigation_test.js b/packages/blockly/tests/mocha/keyboard_navigation_test.js
index 304f1d818b2..e5cffbc7f22 100644
--- a/packages/blockly/tests/mocha/keyboard_navigation_test.js
+++ b/packages/blockly/tests/mocha/keyboard_navigation_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {navigationTestBlocks} from './test_helpers/navigation_test_blocks.js';
 import {p5blocks} from './test_helpers/p5_blocks.js';
 import {
diff --git a/packages/blockly/tests/mocha/layering_test.js b/packages/blockly/tests/mocha/layering_test.js
index b84f23252b3..abd388cfee4 100644
--- a/packages/blockly/tests/mocha/layering_test.js
+++ b/packages/blockly/tests/mocha/layering_test.js
@@ -3,7 +3,7 @@
  * Copyright 2023 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/menu_item_test.js b/packages/blockly/tests/mocha/menu_item_test.js
index fadb9f2c149..7b06f6f2c99 100644
--- a/packages/blockly/tests/mocha/menu_item_test.js
+++ b/packages/blockly/tests/mocha/menu_item_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/metrics_test.js b/packages/blockly/tests/mocha/metrics_test.js
index de9a5641ad7..fc6072e962d 100644
--- a/packages/blockly/tests/mocha/metrics_test.js
+++ b/packages/blockly/tests/mocha/metrics_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/mutator_test.js b/packages/blockly/tests/mocha/mutator_test.js
index 44141ba81b9..9c0260196c3 100644
--- a/packages/blockly/tests/mocha/mutator_test.js
+++ b/packages/blockly/tests/mocha/mutator_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   createRenderedBlock,
   defineMutatorBlocks,
diff --git a/packages/blockly/tests/mocha/names_test.js b/packages/blockly/tests/mocha/names_test.js
index e449a59fd6c..0aa423b8c3f 100644
--- a/packages/blockly/tests/mocha/names_test.js
+++ b/packages/blockly/tests/mocha/names_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/navigation_test.js b/packages/blockly/tests/mocha/navigation_test.js
index 6baa85968c3..003a6deb73d 100644
--- a/packages/blockly/tests/mocha/navigation_test.js
+++ b/packages/blockly/tests/mocha/navigation_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/old_workspace_comment_test.js b/packages/blockly/tests/mocha/old_workspace_comment_test.js
index 5038d67bad8..1b2acf31c60 100644
--- a/packages/blockly/tests/mocha/old_workspace_comment_test.js
+++ b/packages/blockly/tests/mocha/old_workspace_comment_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/procedure_map_test.js b/packages/blockly/tests/mocha/procedure_map_test.js
index 5e29c6ca050..d23b4de14db 100644
--- a/packages/blockly/tests/mocha/procedure_map_test.js
+++ b/packages/blockly/tests/mocha/procedure_map_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {MockProcedureModel} from './test_helpers/procedures.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/rect_test.js b/packages/blockly/tests/mocha/rect_test.js
index 652837eaef6..86b65a48e22 100644
--- a/packages/blockly/tests/mocha/rect_test.js
+++ b/packages/blockly/tests/mocha/rect_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/registry_test.js b/packages/blockly/tests/mocha/registry_test.js
index 2d5e22543ca..436b58d06d4 100644
--- a/packages/blockly/tests/mocha/registry_test.js
+++ b/packages/blockly/tests/mocha/registry_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/render_management_test.js b/packages/blockly/tests/mocha/render_management_test.js
index 8c4844b388c..243a58132ec 100644
--- a/packages/blockly/tests/mocha/render_management_test.js
+++ b/packages/blockly/tests/mocha/render_management_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/serializer_test.js b/packages/blockly/tests/mocha/serializer_test.js
index efd1f308b01..67957adc211 100644
--- a/packages/blockly/tests/mocha/serializer_test.js
+++ b/packages/blockly/tests/mocha/serializer_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   TestCase,
   TestSuite,
diff --git a/packages/blockly/tests/mocha/shortcut_items_test.js b/packages/blockly/tests/mocha/shortcut_items_test.js
index d75141acb9e..3d0ca28d4e5 100644
--- a/packages/blockly/tests/mocha/shortcut_items_test.js
+++ b/packages/blockly/tests/mocha/shortcut_items_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
+import * as Blockly from '#core/blockly.js';
+import {assert} from 'chai';
 import {
   defineRowBlock,
   defineStackBlock,
diff --git a/packages/blockly/tests/mocha/shortcut_registry_test.js b/packages/blockly/tests/mocha/shortcut_registry_test.js
index a7a7c4d8172..28b7180b9d0 100644
--- a/packages/blockly/tests/mocha/shortcut_registry_test.js
+++ b/packages/blockly/tests/mocha/shortcut_registry_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {createTestBlock} from './test_helpers/block_definitions.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/test_helpers/code_generation.js b/packages/blockly/tests/mocha/test_helpers/code_generation.js
index e61a45653b2..e98065482b5 100644
--- a/packages/blockly/tests/mocha/test_helpers/code_generation.js
+++ b/packages/blockly/tests/mocha/test_helpers/code_generation.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {runTestSuites} from './common.js';
 
 /**
diff --git a/packages/blockly/tests/mocha/test_helpers/events.js b/packages/blockly/tests/mocha/test_helpers/events.js
index 8be68127aa4..c7a9118ded1 100644
--- a/packages/blockly/tests/mocha/test_helpers/events.js
+++ b/packages/blockly/tests/mocha/test_helpers/events.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../../node_modules/chai/index.js';
+import {assert} from 'chai';
 
 /**
  * Creates spy for workspace fireChangeListener
diff --git a/packages/blockly/tests/mocha/test_helpers/fields.js b/packages/blockly/tests/mocha/test_helpers/fields.js
index ab304a808a7..f6a63133b68 100644
--- a/packages/blockly/tests/mocha/test_helpers/fields.js
+++ b/packages/blockly/tests/mocha/test_helpers/fields.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {runTestCases, TestCase} from './common.js';
 
 /**
diff --git a/packages/blockly/tests/mocha/test_helpers/icon_mocks.js b/packages/blockly/tests/mocha/test_helpers/icon_mocks.js
index 0e549b9764c..580d727d15a 100644
--- a/packages/blockly/tests/mocha/test_helpers/icon_mocks.js
+++ b/packages/blockly/tests/mocha/test_helpers/icon_mocks.js
@@ -4,10 +4,10 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {isFocusableNode} from '../../../build/src/core/interfaces/i_focusable_node.js';
-import {hasBubble} from '../../../build/src/core/interfaces/i_has_bubble.js';
-import {isIcon} from '../../../build/src/core/interfaces/i_icon.js';
-import {isSerializable} from '../../../build/src/core/interfaces/i_serializable.js';
+import {isFocusableNode} from '#core/interfaces/i_focusable_node.js';
+import {hasBubble} from '#core/interfaces/i_has_bubble.js';
+import {isIcon} from '#core/interfaces/i_icon.js';
+import {isSerializable} from '#core/interfaces/i_serializable.js';
 
 export class MockFocusable {
   getFocusableElement() {}
diff --git a/packages/blockly/tests/mocha/test_helpers/p5_blocks.js b/packages/blockly/tests/mocha/test_helpers/p5_blocks.js
index ad3c6a293e5..0fc6f5df321 100644
--- a/packages/blockly/tests/mocha/test_helpers/p5_blocks.js
+++ b/packages/blockly/tests/mocha/test_helpers/p5_blocks.js
@@ -5,7 +5,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as Blockly from '../../../build/src/core/blockly.js';
+import * as Blockly from '#core/blockly.js';
 
 // p5 Basic Setup Blocks
 
diff --git a/packages/blockly/tests/mocha/test_helpers/procedures.js b/packages/blockly/tests/mocha/test_helpers/procedures.js
index 1573a4bb891..14dc213056d 100644
--- a/packages/blockly/tests/mocha/test_helpers/procedures.js
+++ b/packages/blockly/tests/mocha/test_helpers/procedures.js
@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {ConnectionType} from '../../../build/src/core/connection_type.js';
-import {VariableModel} from '../../../build/src/core/variable_model.js';
-import {assert} from '../../../node_modules/chai/index.js';
+import {ConnectionType} from '#core/connection_type.js';
+import {VariableModel} from '#core/variable_model.js';
+import {assert} from 'chai';
 
 /**
  * Asserts that the procedure definition or call block has the expected var
diff --git a/packages/blockly/tests/mocha/test_helpers/serialization.js b/packages/blockly/tests/mocha/test_helpers/serialization.js
index c476eae3d6f..23e6ebf0cfa 100644
--- a/packages/blockly/tests/mocha/test_helpers/serialization.js
+++ b/packages/blockly/tests/mocha/test_helpers/serialization.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {runTestCases} from './common.js';
 
 /**
diff --git a/packages/blockly/tests/mocha/test_helpers/setup_teardown.js b/packages/blockly/tests/mocha/test_helpers/setup_teardown.js
index b0d7c83c697..fce1ee2a2ff 100644
--- a/packages/blockly/tests/mocha/test_helpers/setup_teardown.js
+++ b/packages/blockly/tests/mocha/test_helpers/setup_teardown.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as eventUtils from '../../../build/src/core/events/utils.js';
-import {FocusManager} from '../../../build/src/core/focus_manager.js';
+import * as eventUtils from '#core/events/utils.js';
+import {FocusManager} from '#core/focus_manager.js';
 
 /**
  * Safely disposes of Blockly workspace, logging any errors.
diff --git a/packages/blockly/tests/mocha/test_helpers/user_input.js b/packages/blockly/tests/mocha/test_helpers/user_input.js
index a5902a7db02..709955af7db 100644
--- a/packages/blockly/tests/mocha/test_helpers/user_input.js
+++ b/packages/blockly/tests/mocha/test_helpers/user_input.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {KeyCodes} from '../../../build/src/core/utils/keycodes.js';
+import {KeyCodes} from '#core/utils/keycodes.js';
 
 /**
  * Triggers pointer event on target.
diff --git a/packages/blockly/tests/mocha/test_helpers/variables.js b/packages/blockly/tests/mocha/test_helpers/variables.js
index 3c6ab9332ae..ce1ad5b9495 100644
--- a/packages/blockly/tests/mocha/test_helpers/variables.js
+++ b/packages/blockly/tests/mocha/test_helpers/variables.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../../node_modules/chai/index.js';
+import {assert} from 'chai';
 
 /**
  * Check if a variable with the given values exists.
diff --git a/packages/blockly/tests/mocha/test_helpers/warnings.js b/packages/blockly/tests/mocha/test_helpers/warnings.js
index d718a25c166..ee7545c6c02 100644
--- a/packages/blockly/tests/mocha/test_helpers/warnings.js
+++ b/packages/blockly/tests/mocha/test_helpers/warnings.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../../node_modules/chai/index.js';
+import {assert} from 'chai';
 
 /**
  * Captures the strings sent to console.warn() when calling a function.
diff --git a/packages/blockly/tests/mocha/test_helpers/workspace.js b/packages/blockly/tests/mocha/test_helpers/workspace.js
index 09e65aefd59..b3ed4da904d 100644
--- a/packages/blockly/tests/mocha/test_helpers/workspace.js
+++ b/packages/blockly/tests/mocha/test_helpers/workspace.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as eventUtils from '../../../build/src/core/events/utils.js';
-import {assert} from '../../../node_modules/chai/index.js';
+import * as eventUtils from '#core/events/utils.js';
+import {assert} from 'chai';
 import {workspaceTeardown} from './setup_teardown.js';
 import {assertVariableValues} from './variables.js';
 
diff --git a/packages/blockly/tests/mocha/theme_test.js b/packages/blockly/tests/mocha/theme_test.js
index f54641a348f..3a91dc294b7 100644
--- a/packages/blockly/tests/mocha/theme_test.js
+++ b/packages/blockly/tests/mocha/theme_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {EventType} from '../../build/src/core/events/type.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {EventType} from '#core/events/type.js';
+import {assert} from 'chai';
 import {assertEventFired} from './test_helpers/events.js';
 import {
   sharedTestSetup,
diff --git a/packages/blockly/tests/mocha/toast_test.js b/packages/blockly/tests/mocha/toast_test.js
index 004b66dce0f..014d546df8b 100644
--- a/packages/blockly/tests/mocha/toast_test.js
+++ b/packages/blockly/tests/mocha/toast_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/toolbox_test.js b/packages/blockly/tests/mocha/toolbox_test.js
index f0f0643774d..ce883c31afd 100644
--- a/packages/blockly/tests/mocha/toolbox_test.js
+++ b/packages/blockly/tests/mocha/toolbox_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   defineBasicBlockWithField,
   defineStackBlock,
diff --git a/packages/blockly/tests/mocha/tooltip_test.js b/packages/blockly/tests/mocha/tooltip_test.js
index 0695b9ebe03..62464bbeb0a 100644
--- a/packages/blockly/tests/mocha/tooltip_test.js
+++ b/packages/blockly/tests/mocha/tooltip_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/touch_test.js b/packages/blockly/tests/mocha/touch_test.js
index 30a9fe72724..1becaae10a6 100644
--- a/packages/blockly/tests/mocha/touch_test.js
+++ b/packages/blockly/tests/mocha/touch_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/trashcan_test.js b/packages/blockly/tests/mocha/trashcan_test.js
index 62486bb5f3e..508d1feaeb5 100644
--- a/packages/blockly/tests/mocha/trashcan_test.js
+++ b/packages/blockly/tests/mocha/trashcan_test.js
@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {EventType} from '../../build/src/core/events/type.js';
-import * as eventUtils from '../../build/src/core/events/utils.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {EventType} from '#core/events/type.js';
+import * as eventUtils from '#core/events/utils.js';
+import {assert} from 'chai';
 import {
   defineBasicBlockWithField,
   defineMutatorBlocks,
diff --git a/packages/blockly/tests/mocha/utils_test.js b/packages/blockly/tests/mocha/utils_test.js
index 0ca3a6fc080..acae9b24d6b 100644
--- a/packages/blockly/tests/mocha/utils_test.js
+++ b/packages/blockly/tests/mocha/utils_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/variable_map_test.js b/packages/blockly/tests/mocha/variable_map_test.js
index 505a221bf80..7fbbfc67aa0 100644
--- a/packages/blockly/tests/mocha/variable_map_test.js
+++ b/packages/blockly/tests/mocha/variable_map_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   assertEventFired,
   assertEventNotFired,
diff --git a/packages/blockly/tests/mocha/variable_model_test.js b/packages/blockly/tests/mocha/variable_model_test.js
index eee7ea9bf41..411d90f1f4a 100644
--- a/packages/blockly/tests/mocha/variable_model_test.js
+++ b/packages/blockly/tests/mocha/variable_model_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/widget_div_test.js b/packages/blockly/tests/mocha/widget_div_test.js
index ef05a19439e..72d013b21b8 100644
--- a/packages/blockly/tests/mocha/widget_div_test.js
+++ b/packages/blockly/tests/mocha/widget_div_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   sharedTestSetup,
   sharedTestTeardown,
diff --git a/packages/blockly/tests/mocha/workspace_comment_test.js b/packages/blockly/tests/mocha/workspace_comment_test.js
index fd4c94f6238..ff1fcba3580 100644
--- a/packages/blockly/tests/mocha/workspace_comment_test.js
+++ b/packages/blockly/tests/mocha/workspace_comment_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   assertEventFired,
   createChangeListenerSpy,
diff --git a/packages/blockly/tests/mocha/workspace_svg_test.js b/packages/blockly/tests/mocha/workspace_svg_test.js
index 4bfc706f916..75d15f61b1c 100644
--- a/packages/blockly/tests/mocha/workspace_svg_test.js
+++ b/packages/blockly/tests/mocha/workspace_svg_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {EventType} from '../../build/src/core/events/type.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {EventType} from '#core/events/type.js';
+import {assert} from 'chai';
 import {defineStackBlock} from './test_helpers/block_definitions.js';
 import {
   assertEventFired,
diff --git a/packages/blockly/tests/mocha/xml_test.js b/packages/blockly/tests/mocha/xml_test.js
index dd871a0008b..0741fa09878 100644
--- a/packages/blockly/tests/mocha/xml_test.js
+++ b/packages/blockly/tests/mocha/xml_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   addBlockTypeToCleanup,
   createGenUidStubWithReturns,
diff --git a/packages/blockly/tests/mocha/zoom_controls_test.js b/packages/blockly/tests/mocha/zoom_controls_test.js
index 8a8ed74c48a..146f0fcbdaf 100644
--- a/packages/blockly/tests/mocha/zoom_controls_test.js
+++ b/packages/blockly/tests/mocha/zoom_controls_test.js
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {EventType} from '../../build/src/core/events/type.js';
-import {assert} from '../../node_modules/chai/index.js';
+import {EventType} from '#core/events/type.js';
+import {assert} from 'chai';
 import {assertEventFired, assertEventNotFired} from './test_helpers/events.js';
 import {
   sharedTestSetup,

From e98f67e1c612e79ea4e4b9c2191457efee29f12e Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Mon, 27 Jul 2026 14:31:22 -0700
Subject: [PATCH 02/13] test: Fix failure in icon test

---
 packages/blockly/tests/mocha/icon_test.js | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/blockly/tests/mocha/icon_test.js b/packages/blockly/tests/mocha/icon_test.js
index 50a3645f05d..e8b57430ba4 100644
--- a/packages/blockly/tests/mocha/icon_test.js
+++ b/packages/blockly/tests/mocha/icon_test.js
@@ -400,6 +400,10 @@ suite('Icon', function () {
       this.block.initSvg();
     });
 
+    teardown(function () {
+      sharedTestTeardown.call(this);
+    });
+
     test('are shown when icons are right clicked', function () {
       const icon = new TestIcon(this.block);
       this.block.addIcon(icon);

From 730d98518dcc4d2505a16905b8fdb12d4897e773 Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Mon, 27 Jul 2026 14:31:41 -0700
Subject: [PATCH 03/13] test: Remove obsolete core tests for the colour field

---
 .../blockly/tests/mocha/field_colour_test.js  | 395 ------------------
 1 file changed, 395 deletions(-)
 delete mode 100644 packages/blockly/tests/mocha/field_colour_test.js

diff --git a/packages/blockly/tests/mocha/field_colour_test.js b/packages/blockly/tests/mocha/field_colour_test.js
deleted file mode 100644
index 975d5a01d4a..00000000000
--- a/packages/blockly/tests/mocha/field_colour_test.js
+++ /dev/null
@@ -1,395 +0,0 @@
-/**
- * @license
- * Copyright 2019 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-import * as Blockly from '../../build/src/core/blockly.js';
-import {assert} from '../../node_modules/chai/index.js';
-import {
-  createTestBlock,
-  defineRowBlock,
-} from './test_helpers/block_definitions.js';
-import {
-  assertFieldValue,
-  runConstructorSuiteTests,
-  runFromJsonSuiteTests,
-  runSetValueTests,
-} from './test_helpers/fields.js';
-import {
-  sharedTestSetup,
-  sharedTestTeardown,
-  workspaceTeardown,
-} from './test_helpers/setup_teardown.js';
-
-suite('Colour Fields', function () {
-  setup(function () {
-    sharedTestSetup.call(this);
-  });
-  teardown(function () {
-    sharedTestTeardown.call(this);
-  });
-  /**
-   * Configuration for field tests with invalid values.
-   * @type {!Array<!FieldCreationTestCase>}
-   */
-  const invalidValueTestCases = [
-    {title: 'Undefined', value: undefined},
-    {title: 'Null', value: null},
-    {title: 'NaN', value: NaN},
-    {title: 'Non-Parsable String', value: 'bad-string'},
-    {title: 'Integer', value: 1},
-    {title: 'Float', value: 1.5},
-    {title: 'Infinity', value: Infinity, expectedValue: Infinity},
-    {title: 'Negative Infinity', value: -Infinity, expectedValue: -Infinity},
-  ];
-  /**
-   * Configuration for field tests with valid values.
-   * @type {!Array<!FieldCreationTestCase>}
-   */
-
-  const validValueTestCases = [
-    {
-      title: '#AAAAAA',
-      value: '#AAAAAA',
-      expectedValue: '#aaaaaa',
-      expectedText: '#aaa',
-    },
-    {
-      title: '#aaaaaa',
-      value: '#aaaaaa',
-      expectedValue: '#aaaaaa',
-      expectedText: '#aaa',
-    },
-    {
-      title: '#AAAA00',
-      value: '#AAAA00',
-      expectedValue: '#aaaa00',
-      expectedText: '#aa0',
-    },
-    {
-      title: '#aaaA00',
-      value: '#aaaA00',
-      expectedValue: '#aaaa00',
-      expectedText: '#aa0',
-    },
-    {
-      title: '#BCBCBC',
-      value: '#BCBCBC',
-      expectedValue: '#bcbcbc',
-      expectedText: '#bcbcbc',
-    },
-    {
-      title: '#bcbcbc',
-      value: '#bcbcbc',
-      expectedValue: '#bcbcbc',
-      expectedText: '#bcbcbc',
-    },
-    {
-      title: '#AA0',
-      value: '#AA0',
-      expectedValue: '#aaaa00',
-      expectedText: '#aa0',
-    },
-    {
-      title: '#aa0',
-      value: '#aa0',
-      expectedValue: '#aaaa00',
-      expectedText: '#aa0',
-    },
-    {
-      title: 'rgb(170, 170, 0)',
-      value: 'rgb(170, 170, 0)',
-      expectedValue: '#aaaa00',
-      expectedText: '#aa0',
-    },
-    {
-      title: 'red',
-      value: 'red',
-      expectedValue: '#ff0000',
-      expectedText: '#f00',
-    },
-  ];
-  const addArgsAndJson = function (testCase) {
-    testCase.args = [testCase.value];
-    testCase.json = {'colour': testCase.value};
-  };
-  invalidValueTestCases.forEach(addArgsAndJson);
-  validValueTestCases.forEach(addArgsAndJson);
-
-  /**
-   * The expected default value for the field being tested.
-   * @type {*}
-   */
-  const defaultFieldValue = Blockly.FieldColour.COLOURS[0];
-  /**
-   * The expected default text for the field being tested.
-   * @type {*}
-   */
-  const defaultTextValue = (function () {
-    let expectedText = defaultFieldValue;
-    const m = defaultFieldValue.match(/^#(.)\1(.)\2(.)\3$/);
-    if (m) {
-      expectedText = '#' + m[1] + m[2] + m[3];
-    }
-    return expectedText;
-  })();
-  /**
-   * Asserts that the field property values are set to default.
-   * @param {FieldTemplate} field The field to check.
-   */
-  const assertFieldDefault = function (field) {
-    assertFieldValue(field, defaultFieldValue, defaultTextValue);
-  };
-  /**
-   * Asserts that the field properties are correct based on the test case.
-   * @param {!Blockly.FieldAngle} field The field to check.
-   * @param {!FieldValueTestCase} testCase The test case.
-   */
-  const validTestCaseAssertField = function (field, testCase) {
-    assertFieldValue(field, testCase.expectedValue, testCase.expectedText);
-  };
-
-  runConstructorSuiteTests(
-    Blockly.FieldColour,
-    validValueTestCases,
-    invalidValueTestCases,
-    validTestCaseAssertField,
-    assertFieldDefault,
-  );
-
-  runFromJsonSuiteTests(
-    Blockly.FieldColour,
-    validValueTestCases,
-    invalidValueTestCases,
-    validTestCaseAssertField,
-    assertFieldDefault,
-  );
-
-  suite('setValue', function () {
-    suite('Empty -> New Value', function () {
-      setup(function () {
-        this.field = new Blockly.FieldColour();
-      });
-      runSetValueTests(
-        validValueTestCases,
-        invalidValueTestCases,
-        defaultFieldValue,
-        defaultTextValue,
-      );
-      test('With source block', function () {
-        this.field.setSourceBlock(createTestBlock());
-        this.field.setValue('#bcbcbc');
-        assertFieldValue(this.field, '#bcbcbc', '#bcbcbc');
-      });
-    });
-    suite('Value -> New Value', function () {
-      setup(function () {
-        this.field = new Blockly.FieldColour('#aaaaaa');
-      });
-      runSetValueTests(
-        validValueTestCases,
-        invalidValueTestCases,
-        '#aaaaaa',
-        '#aaa',
-      );
-      test('With source block', function () {
-        this.field.setSourceBlock(createTestBlock());
-        this.field.setValue('#bcbcbc');
-        assertFieldValue(this.field, '#bcbcbc', '#bcbcbc');
-      });
-    });
-  });
-  suite('Validators', function () {
-    setup(function () {
-      this.field = new Blockly.FieldColour('#aaaaaa');
-    });
-    const testSuites = [
-      {
-        title: 'Null Validator',
-        validator: function () {
-          return null;
-        },
-        value: '#000000',
-        expectedValue: '#aaaaaa',
-        expectedText: '#aaa',
-      },
-      {
-        title: 'Force Full Red Validator',
-        validator: function (newValue) {
-          return '#ff' + newValue.substr(3, 4);
-        },
-        value: '#000000',
-        expectedValue: '#ff0000',
-        expectedText: '#f00',
-      },
-      {
-        title: 'Returns Undefined Validator',
-        validator: function () {},
-        value: '#000000',
-        expectedValue: '#000000',
-        expectedText: '#000',
-      },
-    ];
-    testSuites.forEach(function (suiteInfo) {
-      suite(suiteInfo.title, function () {
-        setup(function () {
-          this.field.setValidator(suiteInfo.validator);
-        });
-        test('New Value', function () {
-          this.field.setValue(suiteInfo.value);
-          assertFieldValue(
-            this.field,
-            suiteInfo.expectedValue,
-            suiteInfo.expectedText,
-          );
-        });
-      });
-    });
-  });
-  suite('Customizations', function () {
-    suite('Colours and Titles', function () {
-      function assertColoursAndTitles(field, colours, titles) {
-        field.dropdownCreate();
-        let index = 0;
-        let node = field.picker.firstChild.firstChild;
-        while (node) {
-          assert.equal(node.getAttribute('title'), titles[index]);
-          assert.equal(
-            Blockly.utils.colour.parse(node.style.backgroundColor),
-            colours[index],
-          );
-
-          let nextNode = node.nextSibling;
-          if (!nextNode) {
-            nextNode = node.parentElement.nextSibling;
-            if (!nextNode) {
-              break;
-            }
-            nextNode = nextNode.firstChild;
-          }
-          node = nextNode;
-
-          index++;
-        }
-      }
-      test('Constants', function () {
-        const colours = Blockly.FieldColour.COLOURS;
-        const titles = Blockly.FieldColour.TITLES;
-        // Note: Developers shouldn't actually do this. IMO they should
-        // change the file and then recompile. But this is fine for testing.
-        Blockly.FieldColour.COLOURS = ['#aaaaaa'];
-        Blockly.FieldColour.TITLES = ['grey'];
-        const field = new Blockly.FieldColour();
-
-        assertColoursAndTitles(field, ['#aaaaaa'], ['grey']);
-
-        Blockly.FieldColour.COLOURS = colours;
-        Blockly.FieldColour.TITLES = titles;
-      });
-      test('JS Constructor', function () {
-        const field = new Blockly.FieldColour('#aaaaaa', null, {
-          colourOptions: ['#aaaaaa'],
-          colourTitles: ['grey'],
-        });
-        assertColoursAndTitles(field, ['#aaaaaa'], ['grey']);
-      });
-      test('JSON Definition', function () {
-        const field = Blockly.FieldColour.fromJson({
-          colour: '#aaaaaa',
-          colourOptions: ['#aaaaaa'],
-          colourTitles: ['grey'],
-        });
-        assertColoursAndTitles(field, ['#aaaaaa'], ['grey']);
-      });
-      test('setColours', function () {
-        const field = new Blockly.FieldColour();
-        field.setColours(['#aaaaaa'], ['grey']);
-        assertColoursAndTitles(field, ['#aaaaaa'], ['grey']);
-      });
-      test('Titles Undefined', function () {
-        const field = new Blockly.FieldColour();
-        field.setColours(['#aaaaaa']);
-        assertColoursAndTitles(field, ['#aaaaaa'], ['#aaaaaa']);
-      });
-      test('Some Titles Undefined', function () {
-        const field = new Blockly.FieldColour();
-        field.setColours(['#aaaaaa', '#ff0000'], ['grey']);
-        assertColoursAndTitles(
-          field,
-          ['#aaaaaa', '#ff0000'],
-          ['grey', '#ff0000'],
-        );
-      });
-      // This is kinda derpy behavior, but I wanted to document it.
-      test('Overwriting Colours While Leaving Titles', function () {
-        const field = new Blockly.FieldColour();
-        field.setColours(['#aaaaaa'], ['grey']);
-        field.setColours(['#ff0000']);
-        assertColoursAndTitles(field, ['#ff0000'], ['grey']);
-      });
-    });
-    suite('Columns', function () {
-      function assertColumns(field, columns) {
-        field.dropdownCreate();
-        assert.equal(field.picker.firstChild.children.length, columns);
-      }
-      test('Constants', function () {
-        const columns = Blockly.FieldColour.COLUMNS;
-        // Note: Developers shouldn't actually do this. IMO they should edit
-        // the file and then recompile. But this is fine for testing.
-        Blockly.FieldColour.COLUMNS = 3;
-        const field = new Blockly.FieldColour();
-
-        assertColumns(field, 3);
-
-        Blockly.FieldColour.COLUMNS = columns;
-      });
-      test('JS Constructor', function () {
-        const field = new Blockly.FieldColour('#ffffff', null, {
-          columns: 3,
-        });
-        assertColumns(field, 3);
-      });
-      test('JSON Definition', function () {
-        const field = Blockly.FieldColour.fromJson({
-          'colour': '#ffffff',
-          'columns': 3,
-        });
-        assertColumns(field, 3);
-      });
-      test('setColumns', function () {
-        const field = new Blockly.FieldColour();
-        field.setColumns(3);
-        assertColumns(field, 3);
-      });
-    });
-  });
-
-  suite('Serialization', function () {
-    setup(function () {
-      this.workspace = new Blockly.Workspace();
-      defineRowBlock();
-
-      this.assertValue = (value) => {
-        const block = this.workspace.newBlock('row_block');
-        const field = new Blockly.FieldColour(value);
-        block.getInput('INPUT').appendField(field, 'COLOUR');
-        const jso = Blockly.serialization.blocks.save(block);
-        assert.deepEqual(jso['fields'], {'COLOUR': value});
-      };
-    });
-
-    teardown(function () {
-      workspaceTeardown.call(this, this.workspace);
-    });
-
-    test('Three char', function () {
-      this.assertValue('#001122');
-    });
-
-    test('Six char', function () {
-      this.assertValue('#012345');
-    });
-  });
-});

From 53a899bf068d412a7bfae953a0f4d7b6357f6e8b Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Tue, 28 Jul 2026 08:32:24 -0700
Subject: [PATCH 04/13] test: Fix missed import

---
 packages/blockly/tests/mocha/dragger_test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/blockly/tests/mocha/dragger_test.js b/packages/blockly/tests/mocha/dragger_test.js
index 7aeb7d84d09..a60f272e4c4 100644
--- a/packages/blockly/tests/mocha/dragger_test.js
+++ b/packages/blockly/tests/mocha/dragger_test.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {assert} from '../../node_modules/chai/index.js';
+import {assert} from 'chai';
 import {
   defineBasicBlockWithField,
   defineStackBlock,

From 7d3a4fb6e37971942b39ffa222926c276d026cfd Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Tue, 28 Jul 2026 08:33:43 -0700
Subject: [PATCH 05/13] fix: Ensure that workspace is still registered before
 focusing it after disposing of a comment

---
 .../blockly/core/comments/rendered_workspace_comment.ts     | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/packages/blockly/core/comments/rendered_workspace_comment.ts b/packages/blockly/core/comments/rendered_workspace_comment.ts
index f60e5bae865..b6eb4541bdd 100644
--- a/packages/blockly/core/comments/rendered_workspace_comment.ts
+++ b/packages/blockly/core/comments/rendered_workspace_comment.ts
@@ -201,7 +201,11 @@ export class RenderedWorkspaceComment
     this.disposing = true;
     const focusManager = getFocusManager();
     if (focusManager.getFocusedNode() === this) {
-      setTimeout(() => focusManager.focusTree(this.workspace), 0);
+      setTimeout(() => {
+        if (focusManager.isRegistered(this.workspace)) {
+          focusManager.focusTree(this.workspace);
+        }
+      }, 0);
     }
     if (!this.view.isDeadOrDying()) this.view.dispose();
 

From ba4cb0dd08b8bfb0cc7f449fae5d8b98507eb99e Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Tue, 28 Jul 2026 10:08:15 -0700
Subject: [PATCH 06/13] test: Fix setup and teardown of parent container in
 tests

---
 packages/blockly/tests/mocha/dropdowndiv_test.js    | 1 +
 packages/blockly/tests/mocha/icon_test.js           | 2 ++
 packages/blockly/tests/mocha/shortcut_items_test.js | 8 ++++++++
 packages/blockly/tests/mocha/widget_div_test.js     | 1 +
 4 files changed, 12 insertions(+)

diff --git a/packages/blockly/tests/mocha/dropdowndiv_test.js b/packages/blockly/tests/mocha/dropdowndiv_test.js
index bc9df1a23b5..84274706d08 100644
--- a/packages/blockly/tests/mocha/dropdowndiv_test.js
+++ b/packages/blockly/tests/mocha/dropdowndiv_test.js
@@ -36,6 +36,7 @@ suite('DropDownDiv', function () {
   teardown(function () {
     sharedTestTeardown.call(this);
     document.getElementById('blocklyDiv').style.visibility = 'hidden';
+    Blockly.common.setParentContainer(null);
   });
 
   suite('Positioning', function () {
diff --git a/packages/blockly/tests/mocha/icon_test.js b/packages/blockly/tests/mocha/icon_test.js
index e8b57430ba4..43c87338fd7 100644
--- a/packages/blockly/tests/mocha/icon_test.js
+++ b/packages/blockly/tests/mocha/icon_test.js
@@ -390,6 +390,7 @@ suite('Icon', function () {
 
   suite('Contextual menus', function () {
     setup(function () {
+      Blockly.common.setParentContainer(document.firstElementChild);
       this.workspace = Blockly.inject('blocklyDiv', {});
       Blockly.icons.registry.register(
         new Blockly.icons.IconType('test'),
@@ -402,6 +403,7 @@ suite('Icon', function () {
 
     teardown(function () {
       sharedTestTeardown.call(this);
+      Blockly.common.setParentContainer(null);
     });
 
     test('are shown when icons are right clicked', function () {
diff --git a/packages/blockly/tests/mocha/shortcut_items_test.js b/packages/blockly/tests/mocha/shortcut_items_test.js
index 3d0ca28d4e5..0077766d247 100644
--- a/packages/blockly/tests/mocha/shortcut_items_test.js
+++ b/packages/blockly/tests/mocha/shortcut_items_test.js
@@ -1924,6 +1924,14 @@ suite('Keyboard Shortcut Items', function () {
       Blockly.utils.KeyCodes.CTRL_CMD,
     ]);
 
+    setup(function () {
+      Blockly.common.setParentContainer(document.firstElementChild);
+    });
+
+    teardown(function () {
+      Blockly.common.setParentContainer(null);
+    });
+
     test('Displays tooltip on a block using the keyboard shortcut', function () {
       const block = this.workspace.newBlock('controls_if');
       Blockly.getFocusManager().focusNode(block);
diff --git a/packages/blockly/tests/mocha/widget_div_test.js b/packages/blockly/tests/mocha/widget_div_test.js
index 72d013b21b8..0d48264308b 100644
--- a/packages/blockly/tests/mocha/widget_div_test.js
+++ b/packages/blockly/tests/mocha/widget_div_test.js
@@ -34,6 +34,7 @@ suite('WidgetDiv', function () {
   teardown(function () {
     sharedTestTeardown.call(this);
     document.getElementById('blocklyDiv').style.visibility = 'hidden';
+    Blockly.common.setParentContainer(null);
   });
 
   suite('positionWithAnchor', function () {

From 9cb244b05e3bc49ca354bc5a22942169b52f7f19 Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Tue, 28 Jul 2026 10:10:13 -0700
Subject: [PATCH 07/13] chore(deps): Add an explicit dep on sinon

---
 package-lock.json             | 120 ++++++++++++++++++++++++++++++++++
 packages/blockly/package.json |   1 +
 2 files changed, 121 insertions(+)

diff --git a/package-lock.json b/package-lock.json
index fd1402fa05b..49648d83df0 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9284,6 +9284,14 @@
         "node": ">=4"
       }
     },
+    "node_modules/@sinonjs/text-encoding": {
+      "version": "0.7.3",
+      "resolved": "https://registry.npmjs.org/@sinonjs/text-encoding/-/text-encoding-0.7.3.tgz",
+      "integrity": "sha512-DE427ROAphMQzU4ENbliGYrBSYPXF+TtLg9S8vzeA+OF4ZKzoDdzfL8sxuMUGS/lgRhM6j1URSk9ghf7Xo1tyA==",
+      "deprecated": "Deprecated: no longer maintained and no longer used by Sinon packages. See\n  https://github.com/sinonjs/nise/issues/243 for replacement details.",
+      "dev": true,
+      "license": "(Unlicense OR Apache-2.0)"
+    },
     "node_modules/@slorber/remark-comment": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/@slorber/remark-comment/-/remark-comment-1.0.0.tgz",
@@ -19910,6 +19918,13 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/just-extend": {
+      "version": "4.2.1",
+      "resolved": "https://registry.npmjs.org/just-extend/-/just-extend-4.2.1.tgz",
+      "integrity": "sha512-g3UB796vUFIY90VIv/WX3L2c8CS2MdWUww3CNrYmqza1Fg0DURc2K/O4YrnklBdQarSJ/y8JnJYDGc+1iumQjg==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/keyv": {
       "version": "4.5.4",
       "resolved": "https://registry.npmjs.org/keyv/-/keyv-4.5.4.tgz",
@@ -20459,6 +20474,14 @@
       "integrity": "sha512-FT1yDzDYEoYWhnSGnpE/4Kj1fLZkDFyqRb7fNt6FdYOSxlUWAtp42Eh6Wb0rGIv/m9Bgo7x4GhQbm5Ys4SG5ow==",
       "license": "MIT"
     },
+    "node_modules/lodash.get": {
+      "version": "4.4.2",
+      "resolved": "https://registry.npmjs.org/lodash.get/-/lodash.get-4.4.2.tgz",
+      "integrity": "sha512-z+Uw/vLuy6gQe8cfaFWD7p0wVv8fJl3mbzXh33RS+0oW2wvUqiRXiQ69gLWSLpgB5/6sU+r6BlQR0MBILadqTQ==",
+      "deprecated": "This package is deprecated. Use the optional chaining (?.) operator instead.",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/lodash.memoize": {
       "version": "4.1.2",
       "resolved": "https://registry.npmjs.org/lodash.memoize/-/lodash.memoize-4.1.2.tgz",
@@ -23469,6 +23492,40 @@
       "dev": true,
       "license": "ISC"
     },
+    "node_modules/nise": {
+      "version": "4.1.0",
+      "resolved": "https://registry.npmjs.org/nise/-/nise-4.1.0.tgz",
+      "integrity": "sha512-eQMEmGN/8arp0xsvGoQ+B1qvSkR73B1nWSCh7nOt5neMCtwcQVYQGdzQMhcNscktTsWB54xnlSQFzOAPJD8nXA==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "@sinonjs/commons": "^1.7.0",
+        "@sinonjs/fake-timers": "^6.0.0",
+        "@sinonjs/text-encoding": "^0.7.1",
+        "just-extend": "^4.0.2",
+        "path-to-regexp": "^1.7.0"
+      }
+    },
+    "node_modules/nise/node_modules/@sinonjs/commons": {
+      "version": "1.8.6",
+      "resolved": "https://registry.npmjs.org/@sinonjs/commons/-/commons-1.8.6.tgz",
+      "integrity": "sha512-Ky+XkAkqPZSm3NLBeUng77EBQl3cmeJhITaGHdYH8kjVB+aun3S4XBRti2zt17mtt0mIUDiNxYeoJm6drVvBJQ==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "type-detect": "4.0.8"
+      }
+    },
+    "node_modules/nise/node_modules/@sinonjs/fake-timers": {
+      "version": "6.0.1",
+      "resolved": "https://registry.npmjs.org/@sinonjs/fake-timers/-/fake-timers-6.0.1.tgz",
+      "integrity": "sha512-MZPUxrmFubI36XS1DI3qmI0YdN1gks62JtFZvxR67ljjSNCeK6U08Zx4msEWOXuofgqUt6zPHSi1H9fbjR/NRA==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "@sinonjs/commons": "^1.7.0"
+      }
+    },
     "node_modules/no-case": {
       "version": "3.0.4",
       "resolved": "https://registry.npmjs.org/no-case/-/no-case-3.0.4.tgz",
@@ -32350,6 +32407,7 @@
         "puppeteer-core": "^25.3.0",
         "readline-sync": "^1.4.10",
         "rimraf": "^6.1.3",
+        "sinon": "^9.2.4",
         "typescript": "^6.0.3",
         "typescript-eslint": "^8.62.1",
         "webdriverio": "^9.30.0",
@@ -32362,6 +32420,38 @@
         "jsdom": ">=27.4.0 <30.0.0"
       }
     },
+    "packages/blockly/node_modules/@sinonjs/commons": {
+      "version": "1.8.6",
+      "resolved": "https://registry.npmjs.org/@sinonjs/commons/-/commons-1.8.6.tgz",
+      "integrity": "sha512-Ky+XkAkqPZSm3NLBeUng77EBQl3cmeJhITaGHdYH8kjVB+aun3S4XBRti2zt17mtt0mIUDiNxYeoJm6drVvBJQ==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "type-detect": "4.0.8"
+      }
+    },
+    "packages/blockly/node_modules/@sinonjs/fake-timers": {
+      "version": "6.0.1",
+      "resolved": "https://registry.npmjs.org/@sinonjs/fake-timers/-/fake-timers-6.0.1.tgz",
+      "integrity": "sha512-MZPUxrmFubI36XS1DI3qmI0YdN1gks62JtFZvxR67ljjSNCeK6U08Zx4msEWOXuofgqUt6zPHSi1H9fbjR/NRA==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "@sinonjs/commons": "^1.7.0"
+      }
+    },
+    "packages/blockly/node_modules/@sinonjs/samsam": {
+      "version": "5.3.1",
+      "resolved": "https://registry.npmjs.org/@sinonjs/samsam/-/samsam-5.3.1.tgz",
+      "integrity": "sha512-1Hc0b1TtyfBu8ixF/tpfSHTVWKwCBLY4QJbkgnE7HcwyvT2xArDxb4K7dMgqRm3szI+LJbzmW/s4xxEhv6hwDg==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "@sinonjs/commons": "^1.6.0",
+        "lodash.get": "^4.4.2",
+        "type-detect": "^4.0.8"
+      }
+    },
     "packages/blockly/node_modules/balanced-match": {
       "version": "4.0.4",
       "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-4.0.4.tgz",
@@ -32385,6 +32475,16 @@
         "node": "20 || >=22"
       }
     },
+    "packages/blockly/node_modules/diff": {
+      "version": "4.0.4",
+      "resolved": "https://registry.npmjs.org/diff/-/diff-4.0.4.tgz",
+      "integrity": "sha512-X07nttJQkwkfKfvTPG/KSnE2OMdcUCao6+eXF3wmnIQRn2aPAHH3VxDbDOdegkd6JbPsXqShpvEOHfAT+nCNwQ==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "engines": {
+        "node": ">=0.3.1"
+      }
+    },
     "packages/blockly/node_modules/glob": {
       "version": "13.0.6",
       "resolved": "https://registry.npmjs.org/glob/-/glob-13.0.6.tgz",
@@ -32446,6 +32546,26 @@
         "url": "https://github.com/sponsors/isaacs"
       }
     },
+    "packages/blockly/node_modules/sinon": {
+      "version": "9.2.4",
+      "resolved": "https://registry.npmjs.org/sinon/-/sinon-9.2.4.tgz",
+      "integrity": "sha512-zljcULZQsJxVra28qIAL6ow1Z9tpattkCTEJR4RBP3TGc00FcttsP5pK284Nas5WjMZU5Yzy3kAIp3B3KRf5Yg==",
+      "deprecated": "16.1.1",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "@sinonjs/commons": "^1.8.1",
+        "@sinonjs/fake-timers": "^6.0.1",
+        "@sinonjs/samsam": "^5.3.1",
+        "diff": "^4.0.2",
+        "nise": "^4.0.4",
+        "supports-color": "^7.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/sinon"
+      }
+    },
     "packages/docs": {
       "name": "blockly-docs",
       "version": "0.0.0",
diff --git a/packages/blockly/package.json b/packages/blockly/package.json
index 71770f31bad..cb1228d5562 100644
--- a/packages/blockly/package.json
+++ b/packages/blockly/package.json
@@ -134,6 +134,7 @@
     "puppeteer-core": "^25.3.0",
     "readline-sync": "^1.4.10",
     "rimraf": "^6.1.3",
+    "sinon": "^9.2.4",
     "typescript": "^6.0.3",
     "typescript-eslint": "^8.62.1",
     "webdriverio": "^9.30.0",

From c9b2024114ead2884c9a0412c2d9c3c22f66e698 Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Wed, 29 Jul 2026 13:30:20 -0700
Subject: [PATCH 08/13] test: Move a few tests depending on browser behavior
 into the browser suite

---
 .../tests/browser/test/dragger_test.mjs       | 373 ++++++++++++++++++
 .../tests/browser/test/dropdowndiv_test.mjs   |  47 +++
 .../tests/browser/test/focus_manager_test.mjs | 295 ++++++++++++++
 packages/blockly/tests/mocha/dragger_test.js  | 303 --------------
 .../blockly/tests/mocha/dropdowndiv_test.js   |  13 -
 .../blockly/tests/mocha/focus_manager_test.js | 178 +--------
 .../mocha/focusable_tree_traverser_test.js    |  58 +--
 .../tests/mocha/test_helpers/dom_fixtures.js  | 196 +++++++++
 .../mocha/test_helpers/focusable_tree.js      |  90 +++++
 9 files changed, 1003 insertions(+), 550 deletions(-)
 create mode 100644 packages/blockly/tests/browser/test/dragger_test.mjs
 create mode 100644 packages/blockly/tests/browser/test/dropdowndiv_test.mjs
 create mode 100644 packages/blockly/tests/browser/test/focus_manager_test.mjs
 delete mode 100644 packages/blockly/tests/mocha/dragger_test.js
 create mode 100644 packages/blockly/tests/mocha/test_helpers/dom_fixtures.js
 create mode 100644 packages/blockly/tests/mocha/test_helpers/focusable_tree.js

diff --git a/packages/blockly/tests/browser/test/dragger_test.mjs b/packages/blockly/tests/browser/test/dragger_test.mjs
new file mode 100644
index 00000000000..9fe0b4ff103
--- /dev/null
+++ b/packages/blockly/tests/browser/test/dragger_test.mjs
@@ -0,0 +1,373 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as chai from 'chai';
+import {testFileLocations, testSetup} from './test_setup.mjs';
+
+suite('Dragging into a delete area', function () {
+  suiteSetup(async function () {
+    this.browser = await testSetup(testFileLocations.PLAYGROUND);
+
+    await this.browser.execute(() => {
+      /**
+       * @param {!Blockly.BlockSvg} block The block to measure.
+       * @returns {{x: number, y: number}} Viewport coordinates at the block center.
+       */
+      window.blockCenterClient = function (block) {
+        const boundingRect = block.getSvgRoot().getBoundingClientRect();
+        return {
+          x: (boundingRect.left + boundingRect.right) / 2,
+          y: (boundingRect.top + boundingRect.bottom) / 2,
+        };
+      };
+
+      /**
+       * @param {!Blockly.BlockSvg} block The block to measure.
+       * @returns {{x: number, y: number}} Viewport coordinates at the block origin.
+       */
+      window.blockOriginClient = function (block) {
+        const ws = block.workspace;
+        let point = block.getRelativeToSurfaceXY();
+        if (ws.isMutator) {
+          point = point.scale(ws.options.parentWorkspace.scale);
+        }
+        const screenCoords = Blockly.utils.svgMath.wsToScreenCoordinates(
+          ws,
+          point,
+        );
+        return {x: screenCoords.x, y: screenCoords.y};
+      };
+
+      /**
+       * Simulates pressing on the block center and dragging to a viewport point.
+       *
+       * @param {!Blockly.BlockSvg} block The block to drag.
+       * @param {{x: number, y: number}} pointerEnd The viewport point to drag to.
+       * @returns {{dragger: !Blockly.dragging.Dragger, dragEvent: !PointerEvent, block: !Blockly.BlockSvg}}
+       *     The dragger, final pointer event, and block being dragged.
+       */
+      window.dragBlock = function (block, pointerEnd) {
+        const start = blockCenterClient(block);
+        const totalDelta = new Blockly.utils.Coordinate(
+          pointerEnd.x - start.x,
+          pointerEnd.y - start.y,
+        );
+
+        const dragger = new Blockly.dragging.Dragger(block);
+        const dragStartEvent = pointerAt(start.x, start.y, 'pointerdown');
+        const dragEvent = pointerAt(pointerEnd.x, pointerEnd.y);
+
+        dragger.onDragStart(dragStartEvent);
+        dragger.onDrag(dragEvent, totalDelta);
+
+        return {dragger, dragEvent, block: dragger.draggable};
+      };
+
+      window.hasDeleteStyle = function (block) {
+        return block.getSvgRoot().classList.contains('blocklyDraggingDelete');
+      };
+
+      /**
+       * @param {number} clientX The viewport x coordinate.
+       * @param {number} clientY The viewport y coordinate.
+       * @param {string=} type The pointer event type.
+       * @returns {!PointerEvent} A synthetic pointer event at the given location.
+       */
+      window.pointerAt = function (clientX, clientY, type = 'pointermove') {
+        return new PointerEvent(type, {clientX, clientY});
+      };
+
+      /**
+       * Opens a mutator on a controls_if block and returns the mutator workspace.
+       *
+       * @param {!Blockly.WorkspaceSvg} workspace The main workspace.
+       * @returns {!Promise<!Blockly.WorkspaceSvg>} The mutator workspace.
+       */
+      window.openMutator = async function (workspace) {
+        const block = Blockly.serialization.blocks.append(
+          {
+            'type': 'controls_if',
+            'extraState': {
+              'elseIfCount': 0,
+            },
+          },
+          workspace,
+        );
+        block.initSvg();
+        block.render();
+        const icon = block.getIcon(Blockly.icons.MutatorIcon.TYPE);
+        await icon.setBubbleVisible(true);
+        return icon.getWorkspace();
+      };
+
+      /**
+       * @param {!Blockly.utils.Rect} rect The rectangle to measure.
+       * @returns {{x: number, y: number}} Viewport coordinates at the rect center.
+       */
+      window.rectCenterClient = function (rect) {
+        return {
+          x: (rect.left + rect.right) / 2,
+          y: (rect.top + rect.bottom) / 2,
+        };
+      };
+
+      /**
+       * @param {!Blockly.WorkspaceSvg} workspace The workspace with a trashcan.
+       * @returns {boolean} Whether the trashcan lid open style is applied.
+       */
+      window.hasTrashLidOpen = function (workspace) {
+        return workspace.trashcan?.svgGroup.classList.contains(
+          'blocklyTrashOpen',
+        );
+      };
+
+      /**
+       * @param {!Blockly.WorkspaceSvg} workspace The workspace to zoom.
+       * @param {number} scale The target zoom factor.
+       */
+      window.setWorkspaceScale = function (workspace, scale) {
+        workspace.setScale(scale);
+      };
+
+      window.getAssertionState = function (block, dragDelta, deleteAreaRect) {
+        const {
+          dragger,
+          dragEvent,
+          block: draggedBlock,
+        } = dragBlock(block, dragDelta);
+
+        const originAfter = blockOriginClient(draggedBlock);
+        const deleteAreaContainsBlockOrigin = deleteAreaRect.contains(
+          originAfter.x,
+          originAfter.y,
+        );
+        const deleteAreaContainsCursor = deleteAreaRect.contains(
+          dragEvent.clientX,
+          dragEvent.clientY,
+        );
+        const blockHasDeleteStyle = hasDeleteStyle(draggedBlock);
+
+        const trashLidOpen = hasTrashLidOpen(draggedBlock.workspace);
+
+        dragger.onDragEnd(dragEvent);
+
+        const blockIsDeadOrDying = draggedBlock.isDeadOrDying();
+
+        return {
+          deleteAreaContainsBlockOrigin,
+          deleteAreaContainsCursor,
+          blockHasDeleteStyle,
+          blockIsDeadOrDying,
+          trashLidOpen,
+        };
+      };
+    });
+  });
+
+  suiteTeardown(async function () {
+    await this.browser.execute(() => {
+      delete window.blockCenterClient;
+      delete window.blockOriginClient;
+      delete window.dragBlock;
+      delete window.hasDeleteStyle;
+      delete window.pointerAt;
+      delete window.openMutator;
+      delete window.rectCenterClient;
+      delete window.hasTrashLidOpen;
+      delete window.setWorkspaceScale;
+      delete window.getAssertionState;
+    });
+  });
+
+  test('does not apply delete styling when only block origin overlaps delete area', async function () {
+    const {
+      deleteAreaContainsBlockOrigin,
+      deleteAreaContainsCursor,
+      blockHasDeleteStyle,
+      blockIsDeadOrDying,
+    } = await this.browser.execute(() => {
+      const block = Blockly.getMainWorkspace().newBlock('controls_if');
+      block.initSvg();
+      block.render();
+
+      const start = blockCenterClient(block);
+      const originBefore = blockOriginClient(block);
+      const deleteAreaRect = Blockly.getMainWorkspace().toolbox.getClientRect();
+      const desiredOrigin = {
+        x: deleteAreaRect.right - 5,
+        y: originBefore.y,
+      };
+      const dragDelta = {
+        x: start.x + desiredOrigin.x - originBefore.x,
+        y: start.y + desiredOrigin.y - originBefore.y,
+      };
+
+      return getAssertionState(block, dragDelta, deleteAreaRect);
+    });
+
+    chai.assert.isTrue(
+      deleteAreaContainsBlockOrigin,
+      'Expected block origin to overlap delete area',
+    );
+    chai.assert.isFalse(
+      deleteAreaContainsCursor,
+      'Expected cursor to be outside delete area',
+    );
+    chai.assert.isFalse(blockHasDeleteStyle);
+    chai.assert.isFalse(blockIsDeadOrDying);
+  });
+
+  test('does not apply delete styling when only block origin overlaps flyout delete area at zoomed scale', async function () {
+    const {
+      flyoutRect,
+      deleteAreaContainsBlockOrigin,
+      deleteAreaContainsCursor,
+      blockHasDeleteStyle,
+      blockIsDeadOrDying,
+    } = await this.browser.execute(async () => {
+      const workspace = Blockly.getMainWorkspace();
+
+      for (let i = 0; i < 3; i++) {
+        workspace.zoomCenter(1);
+      }
+
+      const mutatorWorkspace = await openMutator(workspace);
+      mutatorWorkspace.recordDragTargets();
+
+      const flyout = mutatorWorkspace.getFlyout();
+      const flyoutRect = flyout.getClientRect();
+
+      const workspaceBlock = mutatorWorkspace.newBlock('controls_if_elseif');
+      workspaceBlock.initSvg();
+      workspaceBlock.render();
+      workspaceBlock.moveBy(200, 50);
+
+      const start = blockCenterClient(workspaceBlock);
+      const originBefore = blockOriginClient(workspaceBlock);
+      const desiredOrigin = {
+        x: flyoutRect.right - 5,
+        y: originBefore.y,
+      };
+      const dragDelta = {
+        x: start.x + desiredOrigin.x - originBefore.x,
+        y: start.y + desiredOrigin.y - originBefore.y,
+      };
+
+      return getAssertionState(workspaceBlock, dragDelta, flyoutRect);
+    });
+
+    // chai.assert.isNotNull(flyoutRect);
+    chai.assert.isTrue(
+      deleteAreaContainsBlockOrigin,
+      'Expected block origin to overlap flyout delete area',
+    );
+    chai.assert.isFalse(
+      deleteAreaContainsCursor,
+      'Expected cursor to be outside flyout delete area',
+    );
+    chai.assert.isFalse(blockHasDeleteStyle);
+    chai.assert.isFalse(blockIsDeadOrDying);
+  });
+
+  test('deletes flyout block when pointer is over flyout delete area at zoomed scale', async function () {
+    const {
+      flyoutRect,
+      deleteAreaContainsCursor,
+      blockHasDeleteStyle,
+      blockIsDeadOrDying,
+    } = await this.browser.execute(async () => {
+      const workspace = Blockly.getMainWorkspace();
+
+      for (let i = 0; i < 3; i++) {
+        workspace.zoomCenter(1);
+      }
+
+      const mutatorWorkspace = await openMutator(workspace);
+      mutatorWorkspace.recordDragTargets();
+
+      const flyout = mutatorWorkspace.getFlyout();
+      const flyoutRect = flyout.getClientRect();
+
+      const flyoutBlock = flyout
+        .getWorkspace()
+        .getBlocksByType('controls_if_elseif')[0];
+      flyoutBlock.initSvg();
+      flyoutBlock.render();
+
+      return getAssertionState(
+        flyoutBlock,
+        rectCenterClient(flyoutRect),
+        flyoutRect,
+      );
+    });
+
+    chai.assert.isTrue(
+      deleteAreaContainsCursor,
+      'Expected cursor to be inside flyout delete area',
+    );
+    chai.assert.isTrue(blockHasDeleteStyle);
+    chai.assert.isTrue(blockIsDeadOrDying);
+  });
+
+  const zoomLevels = [
+    {name: 'default scale', scale: null},
+    {name: 'zoomed in', scale: 1.5},
+    {name: 'zoomed out', scale: 0.7},
+  ];
+
+  zoomLevels.forEach(({name: zoomName, scale}) => {
+    [
+      {name: 'trashcan', rectKey: 'trashRect', checkLid: true},
+      {name: 'toolbox', rectKey: 'toolboxRect', checkLid: false},
+    ].forEach(({name, rectKey, checkLid}) => {
+      test(`applies delete styling and deletes when dragged to ${name} at ${zoomName}`, async function () {
+        const {
+          deleteAreaContainsCursor,
+          trashLidOpen,
+          blockHasDeleteStyle,
+          blockIsDeadOrDying,
+        } = await this.browser.execute(
+          (scale, rectKey) => {
+            const workspace = Blockly.getMainWorkspace();
+
+            const block = workspace.newBlock('controls_if');
+            block.initSvg();
+            block.render();
+
+            if (scale !== null) {
+              setWorkspaceScale(workspace, scale);
+              this.trashRect = workspace.trashcan.getClientRect();
+              this.toolboxRect = workspace.toolbox.getClientRect();
+            }
+
+            const deleteRect =
+              rectKey === 'trashRect'
+                ? workspace.trashcan.getClientRect()
+                : workspace.toolbox.getClientRect();
+
+            return getAssertionState(
+              block,
+              rectCenterClient(deleteRect),
+              deleteRect,
+            );
+          },
+          scale,
+          rectKey,
+        );
+
+        chai.assert.isTrue(
+          deleteAreaContainsCursor,
+          `Expected cursor to be inside ${name} delete area`,
+        );
+        chai.assert.isTrue(blockHasDeleteStyle);
+        if (checkLid) {
+          chai.assert.isTrue(trashLidOpen, 'Expected trashcan lid to be open');
+        }
+        chai.assert.isTrue(blockIsDeadOrDying);
+      });
+    });
+  });
+});
diff --git a/packages/blockly/tests/browser/test/dropdowndiv_test.mjs b/packages/blockly/tests/browser/test/dropdowndiv_test.mjs
new file mode 100644
index 00000000000..1842c58c26a
--- /dev/null
+++ b/packages/blockly/tests/browser/test/dropdowndiv_test.mjs
@@ -0,0 +1,47 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as chai from 'chai';
+import {testFileLocations, testSetup} from './test_setup.mjs';
+
+suite('DropDownDiv', function () {
+  suiteSetup(async function () {
+    this.browser = await testSetup(testFileLocations.PLAYGROUND);
+  });
+
+  test('show() with bounds set positions and shows div near specified location', async function () {
+    const result = await this.browser.execute(() => {
+      const workspace = Blockly.getMainWorkspace();
+      Blockly.DropDownDiv.setBoundsElement(document.body);
+      const block = Blockly.serialization.blocks.append(
+        {'type': 'text', 'fields': {'TEXT': ''}},
+        workspace,
+      );
+      const field = Array.from(block.getFields())[0];
+
+      Blockly.DropDownDiv.show(field, false, 50, 60, 70, 80, false);
+
+      const dropDownDivElem = document.querySelector('.blocklyDropDownDiv');
+      const bounds = dropDownDivElem.getBoundingClientRect();
+      return {
+        opacity: dropDownDivElem.style.opacity,
+        left: bounds.left,
+        top: bounds.top,
+        width: bounds.width,
+      };
+    });
+
+    chai.assert.strictEqual(
+      result.opacity,
+      '1',
+      'Expected the div to be shown',
+    );
+    // The div is centered horizontally on the requested x, and its top edge
+    // sits at the requested y.
+    chai.assert.strictEqual(result.left, 50 - result.width / 2);
+    chai.assert.strictEqual(result.top, 60);
+  });
+});
diff --git a/packages/blockly/tests/browser/test/focus_manager_test.mjs b/packages/blockly/tests/browser/test/focus_manager_test.mjs
new file mode 100644
index 00000000000..6dd80918edc
--- /dev/null
+++ b/packages/blockly/tests/browser/test/focus_manager_test.mjs
@@ -0,0 +1,295 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview FocusManager tests that depend on the browser's own focus
+ * handling, and so cannot run in the headless JSDOM harness alongside the rest
+ * of tests/mocha/focus_manager_test.js.
+ *
+ * Two behaviors jsdom does not reproduce are covered here:
+ *
+ * - Detaching the focused element. Browsers reset document.activeElement to
+ *   <body> and fire the corresponding events; JSDOM leaves activeElement
+ *   pointing at the removed element, so FocusManager still reports it as
+ *   focused.
+ * - Moving DOM focus re-entrantly from within a focusin handler. When a tree's
+ *   root receives focus, FocusManager responds by focusing the tree's previously
+ *   focused node instead (see focusTree()). JSDOM does not carry that nested
+ *   focus() through, so the node never becomes active.
+ */
+
+import * as chai from 'chai';
+import {FIXTURE_HTML} from '../../mocha/test_helpers/dom_fixtures.js';
+import {focusableTreeImplFactory} from '../../mocha/test_helpers/focusable_tree.js';
+import {testFileLocations, testSetup} from './test_setup.mjs';
+
+/**
+ * Installs the shared DOM fixtures, the shared FocusableTreeImpl, and the
+ * createFocusableTree/createFocusableNode helpers.
+ *
+ * @param {!WebdriverIO.Browser} browser The active WebdriverIO Browser object.
+ * @param {string} fixtureHtml The shared fixture markup to install.
+ * @return {!Promise} A Promise that resolves once the page is prepared.
+ */
+async function installFocusTestHelpers(browser, fixtureHtml) {
+  await browser.execute(
+    `window.FocusableTreeImpl = (${focusableTreeImplFactory.toString()})();`,
+  );
+
+  await browser.execute((fixtureHtml) => {
+    document.body.insertAdjacentHTML('beforeend', fixtureHtml);
+
+    window.createFocusableTree = function (rootElementId, nestedTrees) {
+      return new window.FocusableTreeImpl(
+        document.getElementById(rootElementId),
+        nestedTrees || [],
+      );
+    };
+    window.createFocusableNode = function (tree, elementId) {
+      return tree.addNode(document.getElementById(elementId));
+    };
+  }, fixtureHtml);
+}
+
+suite('FocusManager', function () {
+  suiteSetup(async function () {
+    this.browser = await testSetup(testFileLocations.PLAYGROUND);
+    await installFocusTestHelpers(this.browser, FIXTURE_HTML);
+  });
+
+  suite('focus*() switching in HTML tree', function () {
+    suite('getFocusedNode()', function () {
+      test('deletion after focusNode() returns null', async function () {
+        const result = await this.browser.execute(() => {
+          const focusManager = Blockly.getFocusManager();
+
+          const rootElem = document.createElement('div');
+          const nodeElem = document.createElement('div');
+          rootElem.setAttribute('id', 'focusRoot');
+          rootElem.setAttribute('tabindex', '-1');
+          nodeElem.setAttribute('id', 'focusNode');
+          nodeElem.setAttribute('tabindex', '-1');
+          nodeElem.textContent = 'Focusable node';
+          rootElem.appendChild(nodeElem);
+          document.body.appendChild(rootElem);
+          const root = createFocusableTree('focusRoot');
+          const node = createFocusableNode(root, 'focusNode');
+          focusManager.registerTree(root);
+          focusManager.focusNode(node);
+          const focusedBeforeDeletion = focusManager.getFocusedNode() === node;
+
+          node.getFocusableElement().remove();
+
+          const focusedAfterDeletion = focusManager.getFocusedNode() === node;
+          focusManager.unregisterTree(root);
+          rootElem.remove(); // Cleanup.
+          return {focusedBeforeDeletion, focusedAfterDeletion};
+        });
+
+        chai.assert.isTrue(
+          result.focusedBeforeDeletion,
+          'Expected focusNode() to have focused the node',
+        );
+        chai.assert.isFalse(
+          result.focusedAfterDeletion,
+          'Expected the deleted node to no longer be focused',
+        );
+      });
+    });
+  });
+
+  suite('DOM focus() switching in HTML tree', function () {
+    suite('getFocusedNode()', function () {
+      test('deletion after focus() returns null', async function () {
+        const result = await this.browser.execute(() => {
+          const focusManager = Blockly.getFocusManager();
+
+          const rootElem = document.createElement('div');
+          const nodeElem = document.createElement('div');
+          rootElem.setAttribute('id', 'focusRoot');
+          rootElem.setAttribute('tabindex', '-1');
+          nodeElem.setAttribute('id', 'focusNode');
+          nodeElem.setAttribute('tabindex', '-1');
+          nodeElem.textContent = 'Focusable node';
+          rootElem.appendChild(nodeElem);
+          document.body.appendChild(rootElem);
+          const root = createFocusableTree('focusRoot');
+          const node = createFocusableNode(root, 'focusNode');
+          focusManager.registerTree(root);
+          document.getElementById('focusNode').tabIndex = -1;
+          document.getElementById('focusNode').focus();
+          const focusedBeforeDeletion = focusManager.getFocusedNode() === node;
+
+          node.getFocusableElement().remove();
+
+          const focusedAfterDeletion = focusManager.getFocusedNode() === node;
+          focusManager.unregisterTree(root);
+          rootElem.remove(); // Cleanup.
+          return {focusedBeforeDeletion, focusedAfterDeletion};
+        });
+
+        chai.assert.isTrue(
+          result.focusedBeforeDeletion,
+          'Expected focus() to have focused the node',
+        );
+        chai.assert.isFalse(
+          result.focusedAfterDeletion,
+          'Expected the deleted node to no longer be focused',
+        );
+      });
+    });
+
+    suite('CSS classes', function () {
+      test('registered tree focus()ed other tree node passively focused tree node now has active property', async function () {
+        const focusClasses = await this.browser.execute(() => {
+          const focusManager = Blockly.getFocusManager();
+          const testFocusableTree1 = createFocusableTree('testFocusableTree1');
+          const testFocusableTree1Node1 = createFocusableNode(
+            testFocusableTree1,
+            'testFocusableTree1.node1',
+          );
+          const testFocusableTree2 = createFocusableTree('testFocusableTree2');
+          createFocusableNode(testFocusableTree2, 'testFocusableTree2.node1');
+
+          focusManager.registerTree(testFocusableTree1);
+          focusManager.registerTree(testFocusableTree2);
+          document.getElementById('testFocusableTree1.node1').tabIndex = -1;
+          document.getElementById('testFocusableTree2.node1').tabIndex = -1;
+          document.getElementById('testFocusableTree1').tabIndex = -1;
+          document.getElementById('testFocusableTree1.node1').focus();
+          document.getElementById('testFocusableTree2.node1').focus();
+
+          document.getElementById('testFocusableTree1').focus();
+
+          // Directly refocusing a tree's root should have functional parity with focusTree(). That
+          // means the tree's previous node should now have active focus again and its root should
+          // have no focus indication.
+          const rootElem = testFocusableTree1
+            .getRootFocusableNode()
+            .getFocusableElement();
+          const nodeElem = testFocusableTree1Node1.getFocusableElement();
+          const {
+            ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
+          } = Blockly.FocusManager;
+          const focusClasses = {
+            nodeActive: nodeElem.classList.contains(
+              ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            ),
+            nodePassive: nodeElem.classList.contains(
+              PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            ),
+            rootActive: rootElem.classList.contains(
+              ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            ),
+            rootPassive: rootElem.classList.contains(
+              PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            ),
+          };
+
+          focusManager.unregisterTree(testFocusableTree1);
+          focusManager.unregisterTree(testFocusableTree2);
+          return focusClasses;
+        });
+
+        chai.assert.isTrue(
+          focusClasses.nodeActive,
+          "Expected the tree's node to have active focus",
+        );
+        chai.assert.isFalse(
+          focusClasses.nodePassive,
+          "Expected the tree's node to not have passive focus",
+        );
+        chai.assert.isFalse(
+          focusClasses.rootActive,
+          "Expected the tree's root to not have active focus",
+        );
+        chai.assert.isFalse(
+          focusClasses.rootPassive,
+          "Expected the tree's root to not have passive focus",
+        );
+      });
+    });
+  });
+
+  suite('DOM focus() switching in SVG tree', function () {
+    suite('CSS classes', function () {
+      test('registered tree focus()ed other tree node passively focused tree node now has active property', async function () {
+        const focusClasses = await this.browser.execute(() => {
+          const focusManager = Blockly.getFocusManager();
+          const testFocusableGroup1 = createFocusableTree(
+            'testFocusableGroup1',
+          );
+          const testFocusableGroup1Node1 = createFocusableNode(
+            testFocusableGroup1,
+            'testFocusableGroup1.node1',
+          );
+          const testFocusableGroup2 = createFocusableTree(
+            'testFocusableGroup2',
+          );
+          createFocusableNode(testFocusableGroup2, 'testFocusableGroup2.node1');
+
+          focusManager.registerTree(testFocusableGroup1);
+          focusManager.registerTree(testFocusableGroup2);
+          document.getElementById('testFocusableGroup1.node1').tabIndex = -1;
+          document.getElementById('testFocusableGroup2.node1').tabIndex = -1;
+          document.getElementById('testFocusableGroup1').tabIndex = -1;
+          document.getElementById('testFocusableGroup1.node1').focus();
+          document.getElementById('testFocusableGroup2.node1').focus();
+
+          document.getElementById('testFocusableGroup1').focus();
+
+          // Directly refocusing a tree's root should have functional parity with focusTree(). That
+          // means the tree's previous node should now have active focus again and its root should
+          // have no focus indication.
+          const rootElem = testFocusableGroup1
+            .getRootFocusableNode()
+            .getFocusableElement();
+          const nodeElem = testFocusableGroup1Node1.getFocusableElement();
+          const {
+            ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
+          } = Blockly.FocusManager;
+          const focusClasses = {
+            nodeActive: nodeElem.classList.contains(
+              ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            ),
+            nodePassive: nodeElem.classList.contains(
+              PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            ),
+            rootActive: rootElem.classList.contains(
+              ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            ),
+            rootPassive: rootElem.classList.contains(
+              PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
+            ),
+          };
+
+          focusManager.unregisterTree(testFocusableGroup1);
+          focusManager.unregisterTree(testFocusableGroup2);
+          return focusClasses;
+        });
+
+        chai.assert.isTrue(
+          focusClasses.nodeActive,
+          "Expected the tree's node to have active focus",
+        );
+        chai.assert.isFalse(
+          focusClasses.nodePassive,
+          "Expected the tree's node to not have passive focus",
+        );
+        chai.assert.isFalse(
+          focusClasses.rootActive,
+          "Expected the tree's root to not have active focus",
+        );
+        chai.assert.isFalse(
+          focusClasses.rootPassive,
+          "Expected the tree's root to not have passive focus",
+        );
+      });
+    });
+  });
+});
diff --git a/packages/blockly/tests/mocha/dragger_test.js b/packages/blockly/tests/mocha/dragger_test.js
deleted file mode 100644
index a60f272e4c4..00000000000
--- a/packages/blockly/tests/mocha/dragger_test.js
+++ /dev/null
@@ -1,303 +0,0 @@
-/**
- * @license
- * Copyright 2026 Raspberry Pi Foundation
- * SPDX-License-Identifier: Apache-2.0
- */
-
-import {assert} from 'chai';
-import {
-  defineBasicBlockWithField,
-  defineStackBlock,
-} from './test_helpers/block_definitions.js';
-import {
-  sharedTestSetup,
-  sharedTestTeardown,
-} from './test_helpers/setup_teardown.js';
-
-suite('Dragger', function () {
-  /**
-   * @param {!Blockly.BlockSvg} block The block to measure.
-   * @returns {{x: number, y: number}} Viewport coordinates at the block center.
-   */
-  function blockCenterClient(block) {
-    const boundingRect = block.getSvgRoot().getBoundingClientRect();
-    return {
-      x: (boundingRect.left + boundingRect.right) / 2,
-      y: (boundingRect.top + boundingRect.bottom) / 2,
-    };
-  }
-
-  /**
-   * @param {!Blockly.BlockSvg} block The block to measure.
-   * @returns {{x: number, y: number}} Viewport coordinates at the block origin.
-   */
-  function blockOriginClient(block) {
-    const ws = block.workspace;
-    let point = block.getRelativeToSurfaceXY();
-    if (ws.isMutator) {
-      point = point.scale(ws.options.parentWorkspace.scale);
-    }
-    const screenCoords = Blockly.utils.svgMath.wsToScreenCoordinates(ws, point);
-    return {x: screenCoords.x, y: screenCoords.y};
-  }
-
-  /**
-   * @param {!Blockly.utils.Rect} rect The rectangle to measure.
-   * @returns {{x: number, y: number}} Viewport coordinates at the rect center.
-   */
-  function rectCenterClient(rect) {
-    return {
-      x: (rect.left + rect.right) / 2,
-      y: (rect.top + rect.bottom) / 2,
-    };
-  }
-
-  /**
-   * @param {number} clientX The viewport x coordinate.
-   * @param {number} clientY The viewport y coordinate.
-   * @param {string=} type The pointer event type.
-   * @returns {!PointerEvent} A synthetic pointer event at the given location.
-   */
-  function pointerAt(clientX, clientY, type = 'pointermove') {
-    return new PointerEvent(type, {clientX, clientY});
-  }
-
-  function hasDeleteStyle(block) {
-    return block.getSvgRoot().classList.contains('blocklyDraggingDelete');
-  }
-
-  /**
-   * @param {!Blockly.WorkspaceSvg} workspace The workspace with a trashcan.
-   * @returns {boolean} Whether the trashcan lid open style is applied.
-   */
-  function hasTrashLidOpen(workspace) {
-    return workspace.trashcan.svgGroup.classList.contains('blocklyTrashOpen');
-  }
-
-  /**
-   * @param {!Blockly.WorkspaceSvg} workspace The workspace to zoom.
-   * @param {number} scale The target zoom factor.
-   */
-  function setWorkspaceScale(workspace, scale) {
-    workspace.setScale(scale);
-  }
-
-  /**
-   * Simulates pressing on the block center and dragging to a viewport point.
-   *
-   * @param {!Blockly.BlockSvg} block The block to drag.
-   * @param {{x: number, y: number}} pointerEnd The viewport point to drag to.
-   * @returns {{dragger: !Blockly.dragging.Dragger, dragEvent: !PointerEvent, block: !Blockly.BlockSvg}}
-   *     The dragger, final pointer event, and block being dragged.
-   */
-  function dragBlock(block, pointerEnd) {
-    const start = blockCenterClient(block);
-    const totalDelta = new Blockly.utils.Coordinate(
-      pointerEnd.x - start.x,
-      pointerEnd.y - start.y,
-    );
-
-    const dragger = new Blockly.dragging.Dragger(block);
-    const dragStartEvent = pointerAt(start.x, start.y, 'pointerdown');
-    const dragEvent = pointerAt(pointerEnd.x, pointerEnd.y);
-
-    dragger.onDragStart(dragStartEvent);
-    dragger.onDrag(dragEvent, totalDelta);
-
-    return {dragger, dragEvent, block: dragger.draggable};
-  }
-
-  setup(function () {
-    sharedTestSetup.call(this);
-    defineBasicBlockWithField();
-    defineStackBlock();
-    const toolbox = document.getElementById('toolbox-categories');
-    this.workspace = Blockly.inject('blocklyDiv', {toolbox, trashcan: true});
-    this.workspace.recordDragTargets();
-    this.trashRect = this.workspace.trashcan.getClientRect();
-    this.toolboxRect = this.workspace.toolbox.getClientRect();
-    assert.isNotNull(this.trashRect);
-    assert.isNotNull(this.toolboxRect);
-
-    this.block = this.workspace.newBlock('stack_block');
-    this.block.initSvg();
-    this.block.render();
-  });
-
-  teardown(function () {
-    sharedTestTeardown.call(this);
-  });
-
-  const zoomLevels = [
-    {name: 'default scale', scale: null},
-    {name: 'zoomed in', scale: 1.5},
-    {name: 'zoomed out', scale: 0.7},
-  ];
-
-  zoomLevels.forEach(({name: zoomName, scale}) => {
-    [
-      {name: 'trashcan', rectKey: 'trashRect', checkLid: true},
-      {name: 'toolbox', rectKey: 'toolboxRect', checkLid: false},
-    ].forEach(({name, rectKey, checkLid}) => {
-      test(`applies delete styling and deletes when dragged to ${name} at ${zoomName}`, function () {
-        if (scale !== null) {
-          setWorkspaceScale(this.workspace, scale);
-          this.trashRect = this.workspace.trashcan.getClientRect();
-          this.toolboxRect = this.workspace.toolbox.getClientRect();
-        }
-
-        const deleteRect = this[rectKey];
-        const {dragger, dragEvent, block} = dragBlock(
-          this.block,
-          rectCenterClient(deleteRect),
-        );
-
-        assert.isTrue(
-          deleteRect.contains(dragEvent.clientX, dragEvent.clientY),
-          `Expected cursor to be inside ${name} delete area`,
-        );
-        assert.isTrue(hasDeleteStyle(block));
-        if (checkLid) {
-          assert.isTrue(
-            hasTrashLidOpen(this.workspace),
-            'Expected trashcan lid to be open',
-          );
-        }
-
-        dragger.onDragEnd(dragEvent);
-        assert.isTrue(block.isDeadOrDying());
-      });
-    });
-  });
-
-  test('does not apply delete styling when only block origin overlaps delete area', function () {
-    const start = blockCenterClient(this.block);
-    const originBefore = blockOriginClient(this.block);
-    const deleteAreaRect = this.toolboxRect;
-    const desiredOrigin = {
-      x: deleteAreaRect.right - 5,
-      y: originBefore.y,
-    };
-    const {dragger, dragEvent, block} = dragBlock(this.block, {
-      x: start.x + desiredOrigin.x - originBefore.x,
-      y: start.y + desiredOrigin.y - originBefore.y,
-    });
-
-    const originAfter = blockOriginClient(block);
-    assert.isTrue(
-      deleteAreaRect.contains(originAfter.x, originAfter.y),
-      'Expected block origin to overlap delete area',
-    );
-    assert.isFalse(
-      deleteAreaRect.contains(dragEvent.clientX, dragEvent.clientY),
-      'Expected cursor to be outside delete area',
-    );
-    assert.isFalse(hasDeleteStyle(block));
-
-    dragger.onDragEnd(dragEvent);
-    assert.isFalse(block.isDeadOrDying());
-  });
-
-  suite('Mutator', function () {
-    /**
-     * Opens a mutator on a controls_if block and returns the mutator workspace.
-     *
-     * @param {!Blockly.WorkspaceSvg} workspace The main workspace.
-     * @returns {!Promise<!Blockly.WorkspaceSvg>} The mutator workspace.
-     */
-    async function openMutator(workspace) {
-      const block = Blockly.serialization.blocks.append(
-        {
-          'type': 'controls_if',
-          'extraState': {
-            'elseIfCount': 0,
-          },
-        },
-        workspace,
-      );
-      block.initSvg();
-      block.render();
-      const icon = block.getIcon(Blockly.icons.MutatorIcon.TYPE);
-      await icon.setBubbleVisible(true);
-      return icon.getWorkspace();
-    }
-
-    test('deletes flyout block when pointer is over flyout delete area at zoomed scale', async function () {
-      for (let i = 0; i < 3; i++) {
-        this.workspace.zoomCenter(1);
-      }
-
-      const mutatorWorkspace = await openMutator(this.workspace);
-      this.clock.runAll();
-      mutatorWorkspace.recordDragTargets();
-
-      const flyout = mutatorWorkspace.getFlyout();
-      const flyoutRect = flyout.getClientRect();
-      assert.isNotNull(flyoutRect);
-
-      const flyoutBlock = flyout
-        .getWorkspace()
-        .getBlocksByType('controls_if_elseif')[0];
-      flyoutBlock.initSvg();
-      flyoutBlock.render();
-
-      const {dragger, dragEvent, block} = dragBlock(
-        flyoutBlock,
-        rectCenterClient(flyoutRect),
-      );
-
-      assert.isTrue(
-        flyoutRect.contains(dragEvent.clientX, dragEvent.clientY),
-        'Expected cursor to be inside flyout delete area',
-      );
-      assert.isTrue(hasDeleteStyle(block));
-
-      dragger.onDragEnd(dragEvent);
-      assert.isTrue(block.isDeadOrDying());
-    });
-
-    test('does not apply delete styling when only block origin overlaps flyout delete area at zoomed scale', async function () {
-      for (let i = 0; i < 3; i++) {
-        this.workspace.zoomCenter(1);
-      }
-
-      const mutatorWorkspace = await openMutator(this.workspace);
-      this.clock.runAll();
-      mutatorWorkspace.recordDragTargets();
-
-      const flyout = mutatorWorkspace.getFlyout();
-      const flyoutRect = flyout.getClientRect();
-      assert.isNotNull(flyoutRect);
-
-      const workspaceBlock = mutatorWorkspace.newBlock('controls_if_elseif');
-      workspaceBlock.initSvg();
-      workspaceBlock.render();
-      workspaceBlock.moveBy(200, 50);
-
-      const start = blockCenterClient(workspaceBlock);
-      const originBefore = blockOriginClient(workspaceBlock);
-      const desiredOrigin = {
-        x: flyoutRect.right - 5,
-        y: originBefore.y,
-      };
-      const {dragger, dragEvent, block} = dragBlock(workspaceBlock, {
-        x: start.x + desiredOrigin.x - originBefore.x,
-        y: start.y + desiredOrigin.y - originBefore.y,
-      });
-
-      const originAfter = blockOriginClient(block);
-      assert.isTrue(
-        flyoutRect.contains(originAfter.x, originAfter.y),
-        'Expected block origin to overlap flyout delete area',
-      );
-      assert.isFalse(
-        flyoutRect.contains(dragEvent.clientX, dragEvent.clientY),
-        'Expected cursor to be outside flyout delete area',
-      );
-      assert.isFalse(hasDeleteStyle(block));
-
-      dragger.onDragEnd(dragEvent);
-      assert.isFalse(block.isDeadOrDying());
-    });
-  });
-});
diff --git a/packages/blockly/tests/mocha/dropdowndiv_test.js b/packages/blockly/tests/mocha/dropdowndiv_test.js
index 84274706d08..2f1c3b9a993 100644
--- a/packages/blockly/tests/mocha/dropdowndiv_test.js
+++ b/packages/blockly/tests/mocha/dropdowndiv_test.js
@@ -183,19 +183,6 @@ suite('DropDownDiv', function () {
       );
     });
 
-    test('with bounds set positions and shows div near specified location', function () {
-      Blockly.DropDownDiv.setBoundsElement(document.body);
-      const block = this.setUpBlockWithField();
-      const field = Array.from(block.getFields())[0];
-
-      Blockly.DropDownDiv.show(field, false, 50, 60, 70, 80, false);
-
-      const dropDownDivElem = document.querySelector('.blocklyDropDownDiv');
-      assert.strictEqual(dropDownDivElem.style.opacity, '1');
-      assert.strictEqual(dropDownDivElem.style.left, '45px');
-      assert.strictEqual(dropDownDivElem.style.top, '60px');
-    });
-
     test('sets the dropdowndiv as owned by the workspace', function () {
       // Set the bounds element explicitly rather than relying on a previous
       // test having set this module-global, so this test is order-independent.
diff --git a/packages/blockly/tests/mocha/focus_manager_test.js b/packages/blockly/tests/mocha/focus_manager_test.js
index 531a1506723..dc47c7ab561 100644
--- a/packages/blockly/tests/mocha/focus_manager_test.js
+++ b/packages/blockly/tests/mocha/focus_manager_test.js
@@ -6,73 +6,12 @@
 
 import {FocusManager, getFocusManager} from '#core/focus_manager.js';
 import {assert} from 'chai';
+import {FocusableTreeImpl} from './test_helpers/focusable_tree.js';
 import {
   sharedTestSetup,
   sharedTestTeardown,
 } from './test_helpers/setup_teardown.js';
 
-class FocusableNodeImpl {
-  constructor(element, tree) {
-    this.element = element;
-    this.tree = tree;
-  }
-
-  getFocusableElement() {
-    return this.element;
-  }
-
-  getFocusableTree() {
-    return this.tree;
-  }
-
-  onNodeFocus() {}
-
-  onNodeBlur() {}
-
-  canBeFocused() {
-    return true;
-  }
-}
-
-class FocusableTreeImpl {
-  constructor(rootElement, nestedTrees) {
-    this.nestedTrees = nestedTrees;
-    this.idToNodeMap = {};
-    this.rootNode = this.addNode(rootElement);
-    this.fallbackNode = null;
-  }
-
-  addNode(element) {
-    const node = new FocusableNodeImpl(element, this);
-    this.idToNodeMap[element.id] = node;
-    return node;
-  }
-
-  removeNode(node) {
-    delete this.idToNodeMap[node.getFocusableElement().id];
-  }
-
-  getRootFocusableNode() {
-    return this.rootNode;
-  }
-
-  getRestoredFocusableNode() {
-    return this.fallbackNode;
-  }
-
-  getNestedTrees() {
-    return this.nestedTrees;
-  }
-
-  lookUpFocusableNode(id) {
-    return this.idToNodeMap[id];
-  }
-
-  onTreeFocus() {}
-
-  onTreeBlur() {}
-}
-
 suite('FocusManager', function () {
   const ACTIVE_FOCUS_NODE_CSS_SELECTOR = `.${FocusManager.ACTIVE_FOCUS_NODE_CSS_CLASS_NAME}`;
   const PASSIVE_FOCUS_NODE_CSS_SELECTOR = `.${FocusManager.PASSIVE_FOCUS_NODE_CSS_CLASS_NAME}`;
@@ -1299,27 +1238,6 @@ suite('FocusManager', function () {
           this.testFocusableNestedTree4Node1,
         );
       });
-
-      test('deletion after focusNode() returns null', function () {
-        const rootElem = document.createElement('div');
-        const nodeElem = document.createElement('div');
-        rootElem.setAttribute('id', 'focusRoot');
-        rootElem.setAttribute('tabindex', '-1');
-        nodeElem.setAttribute('id', 'focusNode');
-        nodeElem.setAttribute('tabindex', '-1');
-        nodeElem.textContent = 'Focusable node';
-        rootElem.appendChild(nodeElem);
-        document.body.appendChild(rootElem);
-        const root = this.createFocusableTree('focusRoot');
-        const node = this.createFocusableNode(root, 'focusNode');
-        this.focusManager.registerTree(root);
-        this.focusManager.focusNode(node);
-
-        node.getFocusableElement().remove();
-
-        assert.notStrictEqual(this.focusManager.getFocusedNode(), node);
-        rootElem.remove(); // Cleanup.
-      });
     });
     suite('CSS classes', function () {
       test('registered tree focusTree()ed no prev focus root elem has active property', function () {
@@ -2287,28 +2205,6 @@ suite('FocusManager', function () {
         );
       });
 
-      test('deletion after focus() returns null', function () {
-        const rootElem = document.createElement('div');
-        const nodeElem = document.createElement('div');
-        rootElem.setAttribute('id', 'focusRoot');
-        rootElem.setAttribute('tabindex', '-1');
-        nodeElem.setAttribute('id', 'focusNode');
-        nodeElem.setAttribute('tabindex', '-1');
-        nodeElem.textContent = 'Focusable node';
-        rootElem.appendChild(nodeElem);
-        document.body.appendChild(rootElem);
-        const root = this.createFocusableTree('focusRoot');
-        const node = this.createFocusableNode(root, 'focusNode');
-        this.focusManager.registerTree(root);
-        document.getElementById('focusNode').tabIndex = -1;
-        document.getElementById('focusNode').focus();
-
-        node.getFocusableElement().remove();
-
-        assert.notStrictEqual(this.focusManager.getFocusedNode(), node);
-        rootElem.remove(); // Cleanup.
-      });
-
       test('after focus() after trying to focusNode() an unfocusable node updates returns focus()ed node', function () {
         this.testFocusableTree1Node1.canBeFocused = () => false;
         document.getElementById('testFocusableTree1.node2').tabIndex = -1;
@@ -2740,42 +2636,6 @@ suite('FocusManager', function () {
         );
       });
 
-      test('registered tree focus()ed other tree node passively focused tree node now has active property', function () {
-        this.focusManager.registerTree(this.testFocusableTree1);
-        this.focusManager.registerTree(this.testFocusableTree2);
-        document.getElementById('testFocusableTree1.node1').tabIndex = -1;
-        document.getElementById('testFocusableTree2.node1').tabIndex = -1;
-        document.getElementById('testFocusableTree1').tabIndex = -1;
-        document.getElementById('testFocusableTree1.node1').focus();
-        document.getElementById('testFocusableTree2.node1').focus();
-
-        document.getElementById('testFocusableTree1').focus();
-
-        // Directly refocusing a tree's root should have functional parity with focusTree(). That
-        // means the tree's previous node should now have active focus again and its root should
-        // have no focus indication.
-        const rootElem = this.testFocusableTree1
-          .getRootFocusableNode()
-          .getFocusableElement();
-        const nodeElem = this.testFocusableTree1Node1.getFocusableElement();
-        assert.includesClass(
-          nodeElem.classList,
-          FocusManager.ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
-        );
-        assert.notIncludesClass(
-          nodeElem.classList,
-          FocusManager.PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
-        );
-        assert.notIncludesClass(
-          rootElem.classList,
-          FocusManager.ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
-        );
-        assert.notIncludesClass(
-          rootElem.classList,
-          FocusManager.PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
-        );
-      });
-
       test('focus on root, node in diff tree, then node in first tree; root should have focus gone', function () {
         this.focusManager.registerTree(this.testFocusableTree1);
         this.focusManager.registerTree(this.testFocusableTree2);
@@ -4708,42 +4568,6 @@ suite('FocusManager', function () {
         );
       });
 
-      test('registered tree focus()ed other tree node passively focused tree node now has active property', function () {
-        this.focusManager.registerTree(this.testFocusableGroup1);
-        this.focusManager.registerTree(this.testFocusableGroup2);
-        document.getElementById('testFocusableGroup1.node1').tabIndex = -1;
-        document.getElementById('testFocusableGroup2.node1').tabIndex = -1;
-        document.getElementById('testFocusableGroup1').tabIndex = -1;
-        document.getElementById('testFocusableGroup1.node1').focus();
-        document.getElementById('testFocusableGroup2.node1').focus();
-
-        document.getElementById('testFocusableGroup1').focus();
-
-        // Directly refocusing a tree's root should have functional parity with focusTree(). That
-        // means the tree's previous node should now have active focus again and its root should
-        // have no focus indication.
-        const rootElem = this.testFocusableGroup1
-          .getRootFocusableNode()
-          .getFocusableElement();
-        const nodeElem = this.testFocusableGroup1Node1.getFocusableElement();
-        assert.includesClass(
-          nodeElem.classList,
-          FocusManager.ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
-        );
-        assert.notIncludesClass(
-          nodeElem.classList,
-          FocusManager.PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
-        );
-        assert.notIncludesClass(
-          rootElem.classList,
-          FocusManager.ACTIVE_FOCUS_NODE_CSS_CLASS_NAME,
-        );
-        assert.notIncludesClass(
-          rootElem.classList,
-          FocusManager.PASSIVE_FOCUS_NODE_CSS_CLASS_NAME,
-        );
-      });
-
       test('focus on root, node in diff tree, then node in first tree; root should have focus gone', function () {
         this.focusManager.registerTree(this.testFocusableGroup1);
         this.focusManager.registerTree(this.testFocusableGroup2);
diff --git a/packages/blockly/tests/mocha/focusable_tree_traverser_test.js b/packages/blockly/tests/mocha/focusable_tree_traverser_test.js
index 84e1bae5342..a59653b6325 100644
--- a/packages/blockly/tests/mocha/focusable_tree_traverser_test.js
+++ b/packages/blockly/tests/mocha/focusable_tree_traverser_test.js
@@ -7,68 +7,12 @@
 import {FocusManager} from '#core/focus_manager.js';
 import {FocusableTreeTraverser} from '#core/utils/focusable_tree_traverser.js';
 import {assert} from 'chai';
+import {FocusableTreeImpl} from './test_helpers/focusable_tree.js';
 import {
   sharedTestSetup,
   sharedTestTeardown,
 } from './test_helpers/setup_teardown.js';
 
-class FocusableNodeImpl {
-  constructor(element, tree) {
-    this.element = element;
-    this.tree = tree;
-  }
-
-  getFocusableElement() {
-    return this.element;
-  }
-
-  getFocusableTree() {
-    return this.tree;
-  }
-
-  onNodeFocus() {}
-
-  onNodeBlur() {}
-
-  canBeFocused() {
-    return true;
-  }
-}
-
-class FocusableTreeImpl {
-  constructor(rootElement, nestedTrees) {
-    this.nestedTrees = nestedTrees;
-    this.idToNodeMap = {};
-    this.rootNode = this.addNode(rootElement);
-  }
-
-  addNode(element) {
-    const node = new FocusableNodeImpl(element, this);
-    this.idToNodeMap[element.id] = node;
-    return node;
-  }
-
-  getRootFocusableNode() {
-    return this.rootNode;
-  }
-
-  getRestoredFocusableNode() {
-    return null;
-  }
-
-  getNestedTrees() {
-    return this.nestedTrees;
-  }
-
-  lookUpFocusableNode(id) {
-    return this.idToNodeMap[id];
-  }
-
-  onTreeFocus() {}
-
-  onTreeBlur() {}
-}
-
 suite('FocusableTreeTraverser', function () {
   setup(function () {
     sharedTestSetup.call(this);
diff --git a/packages/blockly/tests/mocha/test_helpers/dom_fixtures.js b/packages/blockly/tests/mocha/test_helpers/dom_fixtures.js
new file mode 100644
index 00000000000..b4b8853383d
--- /dev/null
+++ b/packages/blockly/tests/mocha/test_helpers/dom_fixtures.js
@@ -0,0 +1,196 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Shared DOM fixtures for the Mocha test suites.
+ */
+
+export const FIXTURE_HTML = `
+  <div id="testFocusableTree1">
+    Focusable tree 1
+    <div id="testFocusableTree1.node1" style="margin-left: 1em">
+      Tree 1 node 1
+      <div id="testFocusableTree1.node1.child1" style="margin-left: 2em">
+        Tree 1 node 1 child 1
+        <div
+          id="testFocusableTree1.node1.child1.unregisteredChild1"
+          style="margin-left: 3em">
+          Tree 1 node 1 child 1 child 1 (unregistered)
+        </div>
+      </div>
+    </div>
+    <div id="testFocusableTree1.node2" style="margin-left: 1em">
+      Tree 1 node 2
+      <div
+        id="testFocusableTree1.node2.unregisteredChild1"
+        style="margin-left: 2em">
+        Tree 1 node 2 child 2 (unregistered)
+      </div>
+    </div>
+    <div id="testFocusableTree1.unregisteredChild1" style="margin-left: 1em">
+      Tree 1 child 1 (unregistered)
+    </div>
+  </div>
+  <div id="testFocusableTree2">
+    Focusable tree 2
+    <div id="testFocusableTree2.node1" style="margin-left: 1em">
+      Tree 2 node 1
+      <div id="testFocusableNestedTree4" style="margin-left: 2em">
+        Nested tree 4
+        <div id="testFocusableNestedTree4.node1" style="margin-left: 3em">
+          Tree 4 node 1 (nested)
+          <div
+            id="testFocusableNestedTree4.node1.unregisteredChild1"
+            style="margin-left: 4em">
+            Tree 4 node 1 child 1 (unregistered)
+          </div>
+        </div>
+      </div>
+    </div>
+    <div id="testFocusableNestedTree5" style="margin-left: 1em">
+      Nested tree 5
+      <div id="testFocusableNestedTree5.node1" style="margin-left: 2em">
+        Tree 5 node 1 (nested)
+      </div>
+    </div>
+  </div>
+  <div id="testUnregisteredFocusableTree3">
+    Unregistered tree 3
+    <div id="testUnregisteredFocusableTree3.node1" style="margin-left: 1em">
+      Tree 3 node 1 (unregistered)
+    </div>
+  </div>
+  <div id="testUnfocusableElement">Unfocusable element</div>
+  <div id="nonTreeElementForEphemeralFocus"></div>
+  <svg width="250" height="250">
+    <g id="testFocusableGroup1">
+      <g id="testFocusableGroup1.node1">
+        <rect x="0" y="0" width="250" height="30" fill="grey" />
+        <text x="10" y="20" class="svgText">Group 1 node 1</text>
+        <g id="testFocusableGroup1.node1.child1">
+          <rect x="0" y="30" width="250" height="30" fill="lightgrey" />
+          <text x="10" y="50" class="svgText">Tree 1 node 1 child 1</text>
+        </g>
+      </g>
+      <g id="testFocusableGroup1.node2">
+        <rect x="0" y="60" width="250" height="30" fill="grey" />
+        <text x="10" y="80" class="svgText">Group 1 node 2</text>
+        <g id="testFocusableGroup1.node2.unregisteredChild1">
+          <rect x="0" y="90" width="250" height="30" fill="lightgrey" />
+          <text x="10" y="110" class="svgText">
+            Tree 1 node 2 child 2 (unregistered)
+          </text>
+        </g>
+      </g>
+    </g>
+    <g id="testFocusableGroup2">
+      <g id="testFocusableGroup2.node1">
+        <rect x="0" y="120" width="250" height="30" fill="grey" />
+        <text x="10" y="140" class="svgText">Group 2 node 1</text>
+      </g>
+      <g id="testFocusableNestedGroup4">
+        <g id="testFocusableNestedGroup4.node1">
+          <rect x="0" y="150" width="250" height="30" fill="lightgrey" />
+          <text x="10" y="170" class="svgText">Group 4 node 1 (nested)</text>
+        </g>
+      </g>
+    </g>
+    <g id="testUnregisteredFocusableGroup3">
+      <g id="testUnregisteredFocusableGroup3.node1">
+        <rect x="0" y="180" width="250" height="30" fill="grey" />
+        <text x="10" y="200" class="svgText">
+          Tree 3 node 1 (unregistered)
+        </text>
+      </g>
+    </g>
+    <g id="nonTreeGroupForEphemeralFocus"></g>
+  </svg>
+
+  <div id="blocklyDiv"></div>
+
+  <xml
+    xmlns="https://developers.google.com/blockly/xml"
+    id="toolbox-simple"
+    style="display: none">
+    <block type="logic_compare">
+      <field name="OP">NEQ</field>
+      <value name="A">
+        <shadow type="math_number">
+          <field name="NUM">1</field>
+        </shadow>
+      </value>
+      <value name="B">
+        <block type="math_number">
+          <field name="NUM">2</field>
+        </block>
+      </value>
+    </block>
+    <sep gap="20"></sep>
+    <button text="insert" callbackkey="insertConnectionRows"></button>
+    <label text="tooltips"></label>
+  </xml>
+
+  <xml
+    xmlns="https://developers.google.com/blockly/xml"
+    id="toolbox-categories"
+    style="display: none">
+    <category name="First" css-container="something">
+      <block type="basic_block">
+        <field name="TEXT">FirstCategory-FirstBlock</field>
+      </block>
+      <block type="basic_block">
+        <field name="TEXT">FirstCategory-SecondBlock</field>
+      </block>
+    </category>
+    <category name="Second">
+      <block type="basic_block">
+        <field name="TEXT">SecondCategory-FirstBlock</field>
+      </block>
+    </category>
+  </xml>
+
+  <xml
+    xmlns="https://developers.google.com/blockly/xml"
+    id="toolbox-test"
+    style="display: none">
+    <category name="First" expanded="true" categorystyle="logic_category">
+      <sep gap="-1"></sep>
+      <button text="insert" callbackkey="insertConnectionRows"></button>
+      <block type="stack_block"></block>
+      <block type="stack_block"></block>
+    </category>
+    <category name="Second">
+      <block type="stack_block"></block>
+    </category>
+    <sep toolboxitemid="separator" gap="-1"></sep>
+    <category name="Variables" custom="VARIABLE"></category>
+    <category name="NestedCategory">
+      <category toolboxitemid="nestedCategory" name="NestedItemOne">
+        <block type="stack_block"></block>
+      </category>
+      <block type="stack_block"></block>
+    </category>
+    <category name="lastItem"></category>
+  </xml>
+
+  <xml
+    xmlns="https://developers.google.com/blockly/xml"
+    id="gesture-test-toolbox"
+    style="display: none">
+    <block type="test_field_block"></block>
+  </xml>
+`;
+
+/**
+ * Installs the shared test fixtures into the given document's body. Safe to
+ * call once per page/document load; calling it again will append a duplicate
+ * set of fixtures, so it should only be invoked during initial harness setup.
+ * @param {!Document} doc The document to install fixtures into. Defaults to the
+ *     ambient `document`.
+ */
+export function installFixtures(doc = document) {
+  doc.body.insertAdjacentHTML('beforeend', FIXTURE_HTML);
+}
diff --git a/packages/blockly/tests/mocha/test_helpers/focusable_tree.js b/packages/blockly/tests/mocha/test_helpers/focusable_tree.js
new file mode 100644
index 00000000000..9b76c74bdd9
--- /dev/null
+++ b/packages/blockly/tests/mocha/test_helpers/focusable_tree.js
@@ -0,0 +1,90 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview A minimal IFocusableTree implementation shared by the focus
+ * tests.
+ */
+
+/**
+ * Builds the test IFocusableTree implementation.
+ *
+ * @returns {!Function} The FocusableTreeImpl class.
+ */
+export function focusableTreeImplFactory() {
+  /** A focusable node wrapping a single element. */
+  class FocusableNodeImpl {
+    constructor(element, tree) {
+      this.element = element;
+      this.tree = tree;
+    }
+
+    getFocusableElement() {
+      return this.element;
+    }
+
+    getFocusableTree() {
+      return this.tree;
+    }
+
+    onNodeFocus() {}
+
+    onNodeBlur() {}
+
+    canBeFocused() {
+      return true;
+    }
+  }
+
+  /**
+   * A focusable tree whose nodes are looked up by element ID.
+   *
+   * Tests can set `fallbackNode` to control getRestoredFocusableNode(), and
+   * override `canBeFocused` on an individual node to make it unfocusable.
+   */
+  class FocusableTreeImpl {
+    constructor(rootElement, nestedTrees = []) {
+      this.nestedTrees = nestedTrees;
+      this.idToNodeMap = {};
+      this.rootNode = this.addNode(rootElement);
+      this.fallbackNode = null;
+    }
+
+    addNode(element) {
+      const node = new FocusableNodeImpl(element, this);
+      this.idToNodeMap[element.id] = node;
+      return node;
+    }
+
+    removeNode(node) {
+      delete this.idToNodeMap[node.getFocusableElement().id];
+    }
+
+    getRootFocusableNode() {
+      return this.rootNode;
+    }
+
+    getRestoredFocusableNode() {
+      return this.fallbackNode;
+    }
+
+    getNestedTrees() {
+      return this.nestedTrees;
+    }
+
+    lookUpFocusableNode(id) {
+      return this.idToNodeMap[id];
+    }
+
+    onTreeFocus() {}
+
+    onTreeBlur() {}
+  }
+
+  return FocusableTreeImpl;
+}
+
+export const FocusableTreeImpl = focusableTreeImplFactory();

From 3523a2a06311a377ca3b7045ac846c50a1b26cb6 Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Wed, 29 Jul 2026 14:17:06 -0700
Subject: [PATCH 09/13] test: Add harness, stubs and command to run Mocha tests
 under Node

---
 packages/blockly/package.json                 |   1 +
 .../blockly/tests/mocha/.mocharc.node.cjs     |  22 ++
 packages/blockly/tests/mocha/node-setup.mjs   | 226 ++++++++++++
 .../mocha/test_helpers/svg_layout_stubs.js    | 334 ++++++++++++++++++
 4 files changed, 583 insertions(+)
 create mode 100644 packages/blockly/tests/mocha/.mocharc.node.cjs
 create mode 100644 packages/blockly/tests/mocha/node-setup.mjs
 create mode 100644 packages/blockly/tests/mocha/test_helpers/svg_layout_stubs.js

diff --git a/packages/blockly/package.json b/packages/blockly/package.json
index cb1228d5562..e2243ffb897 100644
--- a/packages/blockly/package.json
+++ b/packages/blockly/package.json
@@ -46,6 +46,7 @@
     "tsc": "gulp tsc",
     "test": "gulp test",
     "test:browser": "npx mocha --config tests/browser/.mocharc.js",
+    "test:mocha:node": "npx mocha --config tests/mocha/.mocharc.node.cjs \"tests/mocha/**/*_test.js\"",
     "test:generators": "gulp testGenerators",
     "test:mocha:interactive": "npm run build && concurrently -n tsc,server \"tsc --watch --preserveWatchOutput --outDir \"build/src\" --declarationDir \"build/declarations\"\" \"gulp interactiveMocha\"",
     "test:compile:advanced": "gulp buildAdvancedCompilationTest --debug",
diff --git a/packages/blockly/tests/mocha/.mocharc.node.cjs b/packages/blockly/tests/mocha/.mocharc.node.cjs
new file mode 100644
index 00000000000..ee49831778b
--- /dev/null
+++ b/packages/blockly/tests/mocha/.mocharc.node.cjs
@@ -0,0 +1,22 @@
+'use strict';
+
+/**
+ * Mocha configuration for running the Blockly unit suite headless under Node +
+ * jsdom. See tests/mocha/node-setup.mjs for the DOM/global bootstrap.
+ *
+ * To run or debug a single file:
+ *
+ *   npx mocha --config tests/mocha/.mocharc.node.cjs tests/mocha/foo_test.js
+ *
+ * Console output from the tests is suppressed; set BLOCKLY_TEST_CONSOLE=1 to
+ * see it. See tests/mocha/node-setup.mjs.
+ */
+
+module.exports = {
+  ui: 'tdd',
+  reporter: 'spec',
+  parallel: true,
+  require: ['./tests/mocha/node-setup.mjs'],
+  timeout: 10000,
+  exit: true,
+};
diff --git a/packages/blockly/tests/mocha/node-setup.mjs b/packages/blockly/tests/mocha/node-setup.mjs
new file mode 100644
index 00000000000..d4a33102477
--- /dev/null
+++ b/packages/blockly/tests/mocha/node-setup.mjs
@@ -0,0 +1,226 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Mocha root setup for running the Blockly unit suite headless
+ * under Node using JSDom.
+ *
+ * It registers a JSDom DOM, browser globals the tests and Blockly
+ * expect, installs the geometry stubs JSDom lacks, exposes sinon as a global,
+ * loads Blockly + the standard blocks + the JavaScript generator, and installs
+ * the shared DOM fixtures. The same fixtures and tests run in the browser via
+ * `npm run test:mocha:interactive`.
+ */
+
+import {config as chaiConfig} from 'chai';
+import {JSDOM} from 'jsdom';
+import {readFileSync} from 'node:fs';
+import {createRequire} from 'node:module';
+import vm from 'node:vm';
+import sinon from 'sinon';
+import {installFixtures} from './test_helpers/dom_fixtures.js';
+import {
+  HEADLESS_VIEWPORT_SIZE,
+  installSvgLayoutStubs,
+} from './test_helpers/svg_layout_stubs.js';
+
+const buildDir = `${import.meta.dirname}/../../build`;
+
+// Create the DOM. The "localhost" URL makes tests/scripts/load.mjs select
+// uncompressed mode (importing build/src/**), matching the browser file:// run.
+const dom = new JSDOM(
+  '<!doctype html><html><body tabindex="-1"></body></html>',
+  {
+    pretendToBeVisual: true,
+    url: 'http://localhost/tests/mocha/index.html',
+  },
+);
+const {window} = dom;
+
+/**
+ * Defines a global property, overriding read-only Node built-ins (e.g.
+ * navigator, location, Event) with the JSDom equivalents.
+ * @param {string} name The global name.
+ * @param {*} value The value to assign.
+ */
+function defineGlobal(name, value) {
+  Object.defineProperty(globalThis, name, {
+    value,
+    configurable: true,
+    writable: true,
+  });
+}
+
+/**
+ * Whether a global of this name can be replaced.
+ *
+ * Some properties, like `Infinity` and `NaN` are non-configurable on Node's
+ * global object, so attempting to overwrite them in defineGlobal() throws.
+ *
+ * @param {string} name The global name.
+ * @return {boolean} Whether defineGlobal() can safely define it.
+ */
+function isRedefinableGlobal(name) {
+  const descriptor = Object.getOwnPropertyDescriptor(globalThis, name);
+  return !descriptor || descriptor.configurable;
+}
+
+/**
+ * Window members that Blockly and the tests use unqualified.
+ *
+ * Blockly's source was written for a browser, where `window` is the global
+ * object, so it uses `document`, `requestAnimationFrame(...)`, etc. without the
+ * `window.` prefix. Under Node globalThis is not JSDom's window, so those names
+ * have to be copied across for the code to resolve them.
+ *
+ * Unlike the DOM interfaces below, these are listed explicitly rather than
+ * derived, because bulk-copying everything lowercase off the window would be
+ * problematic, as some of them collide with globals Node already provides, and
+ * may throw or conflict with sinon's patches. If a ReferenceError for something
+ * that lives on window is encountered in the tests, it should likely be added
+ * here.
+ * @constant {!Array<string>}
+ */
+const WINDOW_MEMBERS = [
+  'window',
+  'document',
+  'navigator',
+  'location',
+  'history',
+  'customElements',
+  'getComputedStyle',
+  'getSelection',
+  'requestAnimationFrame',
+  'cancelAnimationFrame',
+];
+
+/**
+ * Collects the DOM interfaces JSDom exposes (Node, Element, etc), so
+ * that a test needing one does not first have to register it here.
+ *
+ * They are identified by their leading capital, which is the naming convention
+ * for interfaces in every Web Interface Definition Language spec; everything
+ * lowercase is a window member, handled by WINDOW_MEMBERS above.
+ * @param {!Window} win The JSDom window.
+ * @return {!Array<string>} The interface names to install.
+ */
+function domInterfaceNames(win) {
+  const names = new Set();
+  // Walk the prototype chain too: JSDom defines some of these on
+  // Window.prototype rather than on the window object itself.
+  for (let obj = win; obj; obj = Object.getPrototypeOf(obj)) {
+    for (const name of Object.getOwnPropertyNames(obj)) {
+      if (/^[A-Z]/.test(name) && isRedefinableGlobal(name)) {
+        names.add(name);
+      }
+    }
+  }
+  return [...names];
+}
+
+// Only what JSDom actually provides is installed; anything it does not
+// implement (matchMedia, ResizeObserver, etc) is skipped, and a test
+// that needs one has to stub it.
+for (const name of [...domInterfaceNames(window), ...WINDOW_MEMBERS]) {
+  if (window[name] !== undefined) {
+    defineGlobal(name, window[name]);
+  }
+}
+
+// Tests use sinon and chai's config as ambient globals (sinon) / shared config.
+globalThis.sinon = sinon;
+chaiConfig.showDiff = false;
+
+// Silence console output from the tests and from Blockly itself.
+//
+// A number of tests deliberately drive error paths that log, or inadvertently
+// trigger logging, and workspaceTeardown() reports the errors it swallows, so
+// running the tests is quite noisy.
+//
+// Set BLOCKLY_TEST_CONSOLE=1 to see the output when debugging.
+if (!process.env.BLOCKLY_TEST_CONSOLE) {
+  for (const method of ['log', 'info', 'warn', 'error', 'debug', 'trace']) {
+    console[method] = () => {};
+  }
+}
+
+// Make sinon's fake clock advance with real time.
+//
+// sharedTestSetup() freezes the clock, and JSDom drives requestAnimationFrame
+// off setTimeout, so frames only run when something advances the clock. The
+// only thing that does so mid-test is the Events.fire stub's clock.runAll(), so
+// a queueRender() landing after the last fired event leaves its frame unrun —
+// and with it the finishQueuedRenders() promise it would resolve. Any test
+// awaiting that promise then hangs until teardown. Advancing with real time
+// keeps frames flowing without giving up the clock's manual tick/runAll
+// control, which tests still rely on.
+//
+// Browsers do not need this: there, sinon fakes requestAnimationFrame itself
+// rather than JSDom's setTimeout-backed one, so the browser harness (which does
+// not load this file) is unaffected.
+const createSandbox = sinon.createSandbox.bind(sinon);
+sinon.createSandbox = function (...args) {
+  const sandbox = createSandbox(...args);
+  const useFakeTimers = sandbox.useFakeTimers.bind(sandbox);
+  sandbox.useFakeTimers = (config = {}) =>
+    useFakeTimers({...config, shouldAdvanceTime: true});
+  return sandbox;
+};
+
+// Install geometry stubs (getBBox/getCTM/getScreenCTM/createSVGPoint, canvas
+// text measurement) that JSDom does not implement.
+installSvgLayoutStubs(window);
+
+// Load Blockly, the standard blocks and the JavaScript generator, and expose
+// them as globals, mirroring what tests/mocha/index.html does in the browser.
+const Blockly = await import('../../build/blockly.loader.mjs');
+await import('../../build/blocks.loader.mjs');
+const {javascriptGenerator} = await import('../../build/javascript.loader.mjs');
+
+globalThis.Blockly = Blockly;
+globalThis.javascriptGenerator = javascriptGenerator;
+
+// Load English messages. build/msg/en.js is a classic script (not a module)
+// that augments the global Blockly.Msg, exactly as the browser harness loads it
+// via a <script> tag. Run it in the global context so its top-level
+// `var Blockly = Blockly || ...` picks up the global Blockly just set.
+vm.runInThisContext(readFileSync(`${buildDir}/msg/en.js`, 'utf8'));
+
+// Register the shared test blocks (test_fields_*, test_dropdowns_*, etc.) that
+// many suites rely on.
+const require = createRequire(import.meta.url);
+vm.runInThisContext(
+  readFileSync(require.resolve('@blockly/block-test'), 'utf8'),
+);
+
+// Install the shared DOM fixtures now that Blockly is loaded.
+installFixtures(window.document);
+
+// The browser harness sizes #blocklyDiv with CSS; JSDom applies no layout, so
+// set it explicitly. Everything Blockly injects inside it is sized in
+// percentages and resolves against this via the stubs installed above.
+const blocklyDiv = window.document.getElementById('blocklyDiv');
+blocklyDiv.style.width = `${HEADLESS_VIEWPORT_SIZE.width}px`;
+blocklyDiv.style.height = `${HEADLESS_VIEWPORT_SIZE.height}px`;
+
+/**
+ * Root hook plugin: reset DOM focus between tests.
+ *
+ * JSDom does not reset document.activeElement when the focused element is
+ * removed from the document, so disposing a workspace can leave one of its
+ * fields focused. The next test then starts with a stale activeElement, and
+ * showing a popup fires a focusout from outside the current workspace, which
+ * FocusManager reads as the popover losing focus and hides it mid-show.
+ *
+ * Browsers reset activeElement to <body> when the focused element is detached,
+ * so the browser harness (which does not load this file) needs no equivalent.
+ */
+export const mochaHooks = {
+  afterEach() {
+    const active = window.document.activeElement;
+    if (active && active !== window.document.body) active.blur?.();
+  },
+};
diff --git a/packages/blockly/tests/mocha/test_helpers/svg_layout_stubs.js b/packages/blockly/tests/mocha/test_helpers/svg_layout_stubs.js
new file mode 100644
index 00000000000..79da167ef1d
--- /dev/null
+++ b/packages/blockly/tests/mocha/test_helpers/svg_layout_stubs.js
@@ -0,0 +1,334 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Geometry stubs for running the Mocha suite under JSDom.
+ *
+ * JSDom implements the SVG DOM but not SVG layout: it provides no `getBBox`,
+ * `getCTM`, `getScreenCTM` or `createSVGPoint`, and `HTMLCanvasElement` has no
+ * 2D context (so text measurement returns 0). Blockly's rendering calls these
+ * APIs, so without stubs an injected workspace throws.
+ *
+ * These stubs provide deterministic, non-zero, internally consistent geometry
+ * so that layout math does not divide by zero or dereference null matrices.
+ * They are NOT pixel-accurate; tests that assert exact rendered coordinates
+ * belong in the webdriver suite under tests/browser instead, where they run
+ * against a real browser's layout.
+ */
+
+/** Approximate width in px of a single character, for text measurement. */
+const CHAR_WIDTH = 8;
+
+/**
+ * Size in px reported for the headless viewport.
+ */
+export const HEADLESS_VIEWPORT_SIZE = {width: 1000, height: 1000};
+
+/**
+ * Reads an explicit px size off an element's inline style.
+ * @param {!Element} element The element to read.
+ * @param {string} property Either 'width' or 'height'.
+ * @return {?number} The size in px, or null if not set in px.
+ */
+function explicitPx(element, property) {
+  const value = element.style?.[property];
+  if (typeof value !== 'string' || !value.endsWith('px')) return null;
+  const px = Number.parseFloat(value);
+  return Number.isFinite(px) ? px : null;
+}
+
+/**
+ * Resolves the layout size of an element for the offset/client size stubs.
+ *
+ * JSDom performs no layout, so it reports 0 for every offsetWidth/clientWidth.
+ * Blockly derives its viewport metrics from those (svgResize() in
+ * core/common.ts reads the injection div's offsetWidth), and a zero viewport
+ * minus a real toolbox width yields a negative-width scroll region, which makes
+ * bumpObjectIntoBounds() unable to ever settle. So resolve a size from the
+ * nearest ancestor with an explicit px size — Blockly's own injection div and
+ * SVG are sized 100%, and inherit the fixed size given to #blocklyDiv.
+ *
+ * Elements with no sized ancestor still report 0, as they do today.
+ * @param {!Element} element The element to size.
+ * @param {string} property Either 'width' or 'height'.
+ * @return {number} The resolved size in px.
+ */
+function resolveLayoutSize(element, property) {
+  for (let node = element; node; node = node.parentElement) {
+    const px = explicitPx(node, property);
+    if (px !== null) return px;
+  }
+  return 0;
+}
+
+/**
+ * Defines a size getter that resolves through ancestors, replacing JSDom's
+ * always-zero implementation.
+ * @param {!Object} proto The prototype to patch.
+ * @param {string} name The property to define, e.g. 'offsetWidth'.
+ * @param {string} property Either 'width' or 'height'.
+ */
+function defineSizeGetter(proto, name, property) {
+  if (!proto) return;
+  Object.defineProperty(proto, name, {
+    configurable: true,
+    get() {
+      return resolveLayoutSize(this, property);
+    },
+  });
+}
+
+/**
+ * Minimal 2D affine matrix supporting the operations Blockly performs on the
+ * results of getCTM/getScreenCTM (inverse, translate, scale).
+ */
+class FakeMatrix {
+  /**
+   * @param {number=} a Horizontal scaling.
+   * @param {number=} b Vertical skewing.
+   * @param {number=} c Horizontal skewing.
+   * @param {number=} d Vertical scaling.
+   * @param {number=} e Horizontal translation.
+   * @param {number=} f Vertical translation.
+   */
+  constructor(a = 1, b = 0, c = 0, d = 1, e = 0, f = 0) {
+    this.a = a;
+    this.b = b;
+    this.c = c;
+    this.d = d;
+    this.e = e;
+    this.f = f;
+  }
+
+  /**
+   * @param {!FakeMatrix} m The matrix to multiply by (this * m).
+   * @return {!FakeMatrix} The product.
+   */
+  multiply(m) {
+    return new FakeMatrix(
+      this.a * m.a + this.c * m.b,
+      this.b * m.a + this.d * m.b,
+      this.a * m.c + this.c * m.d,
+      this.b * m.c + this.d * m.d,
+      this.a * m.e + this.c * m.f + this.e,
+      this.b * m.e + this.d * m.f + this.f,
+    );
+  }
+
+  /** @return {!FakeMatrix} The inverse of this affine matrix. */
+  inverse() {
+    const det = this.a * this.d - this.b * this.c;
+    if (!det) {
+      // Singular matrix; return identity rather than producing NaNs.
+      return new FakeMatrix();
+    }
+    const a = this.d / det;
+    const b = -this.b / det;
+    const c = -this.c / det;
+    const d = this.a / det;
+    return new FakeMatrix(
+      a,
+      b,
+      c,
+      d,
+      -(a * this.e + c * this.f),
+      -(b * this.e + d * this.f),
+    );
+  }
+
+  /**
+   * @param {number} x Horizontal translation.
+   * @param {number} y Vertical translation.
+   * @return {!FakeMatrix} A new translated matrix.
+   */
+  translate(x, y) {
+    return this.multiply(new FakeMatrix(1, 0, 0, 1, x, y));
+  }
+
+  /**
+   * @param {number} factor Uniform scale factor.
+   * @return {!FakeMatrix} A new scaled matrix.
+   */
+  scale(factor) {
+    return this.multiply(new FakeMatrix(factor, 0, 0, factor, 0, 0));
+  }
+}
+
+/**
+ * @param {!Element} element The element to derive a bounding box for.
+ * @return {{x: number, y: number, width: number, height: number}} A
+ *     deterministic, non-zero box sized from the element's text content.
+ */
+function fakeBBox(element) {
+  const text = element.textContent || '';
+  return {
+    x: 0,
+    y: 0,
+    width: Math.max(text.length * CHAR_WIDTH, 1),
+    height: 16,
+  };
+}
+
+/** Minimal 2D canvas context exposing only what dom.js text measurement uses. */
+class FakeCanvasContext {
+  constructor() {
+    this.font = '';
+  }
+
+  /**
+   * @param {string} text The text to measure.
+   * @return {{width: number}} An approximate text metrics object.
+   */
+  measureText(text) {
+    return {width: (text ? text.length : 0) * CHAR_WIDTH};
+  }
+}
+
+/**
+ * Installs geometry stubs onto the given JSDom window's prototypes. Should be
+ * called once during Node harness setup, before any workspace is injected.
+ * @param {!Window} window The JSDom window whose prototypes to patch.
+ */
+export function installSvgLayoutStubs(window) {
+  // getBBox/getCTM/getScreenCTM are spec'd on SVGGraphicsElement, but JSDom's
+  // SVG class hierarchy is incomplete (e.g. <rect> is a bare SVGElement, not an
+  // SVGGraphicsElement), so patch the SVGElement base to cover every element.
+  const element = window.Element?.prototype;
+  const svgElement = window.SVGElement?.prototype;
+  const svg = window.SVGSVGElement?.prototype;
+  const canvas = window.HTMLCanvasElement?.prototype;
+
+  // Element.checkVisibility() is a newer DOM API JSDom does not implement.
+  // Treat every element as visible in the headless layout.
+  if (element && !element.checkVisibility) {
+    element.checkVisibility = function () {
+      return true;
+    };
+  }
+
+  // getElementById is only defined on Document/ShadowRoot. Blockly calls it on
+  // the result of getRootNode(), which can be a detached SVG element during
+  // disposal. Provide a descendant search so those code paths work headless.
+  if (element && !element.getElementById) {
+    element.getElementById = function (id) {
+      const stack = [...this.children];
+      while (stack.length) {
+        const el = stack.shift();
+        if (el.getAttribute && el.getAttribute('id') === id) return el;
+        stack.push(...el.children);
+      }
+      return null;
+    };
+  }
+
+  // JSDom does not implement HTMLElement.innerText; approximate it with
+  // textContent (sufficient for tests that assert on rendered menu text).
+  const htmlElement = window.HTMLElement?.prototype;
+  if (
+    htmlElement &&
+    !Object.getOwnPropertyDescriptor(htmlElement, 'innerText')
+  ) {
+    Object.defineProperty(htmlElement, 'innerText', {
+      configurable: true,
+      get() {
+        return this.textContent;
+      },
+      set(value) {
+        this.textContent = value;
+      },
+    });
+  }
+
+  // JSDom does not implement the <dialog> showModal/show/close methods.
+  const dialog = window.HTMLDialogElement?.prototype;
+  if (dialog && !dialog.showModal) {
+    const open = function () {
+      this.open = true;
+      this.setAttribute('open', '');
+    };
+    dialog.showModal = open;
+    dialog.show = open;
+    dialog.close = function (returnValue) {
+      this.open = false;
+      this.removeAttribute('open');
+      if (returnValue !== undefined) this.returnValue = returnValue;
+      this.dispatchEvent(new window.Event('close'));
+    };
+  }
+
+  // JSDom does not implement submission of a <form method="dialog">, which is
+  // how Blockly's built-in alert/confirm/prompt dialogs close (a button click
+  // submits the form, closing the dialog with the button's value). Emulate it
+  // so those dialogs behave headless as they do in a browser.
+  window.document.addEventListener(
+    'click',
+    (event) => {
+      const button = event.target.closest?.('button');
+      if (!button || button.type === 'button') return;
+      const form = button.closest('form[method="dialog" i]');
+      const dialogEl = form?.closest('dialog');
+      if (dialogEl) {
+        event.preventDefault();
+        dialogEl.close(button.value ?? '');
+      }
+    },
+    true,
+  );
+
+  if (svgElement && !svgElement.getBBox) {
+    svgElement.getBBox = function () {
+      return fakeBBox(this);
+    };
+  }
+  if (svgElement && !svgElement.getCTM) {
+    svgElement.getCTM = function () {
+      return new FakeMatrix();
+    };
+  }
+  if (svgElement && !svgElement.getScreenCTM) {
+    svgElement.getScreenCTM = function () {
+      return new FakeMatrix();
+    };
+  }
+  if (svg && !svg.createSVGPoint) {
+    svg.createSVGPoint = function () {
+      return {
+        x: 0,
+        y: 0,
+        matrixTransform(m) {
+          return {
+            x: m.a * this.x + m.c * this.y + m.e,
+            y: m.b * this.x + m.d * this.y + m.f,
+          };
+        },
+      };
+    };
+  }
+
+  // Viewport size: clientWidth/clientHeight live on Element (the workspace
+  // reads them off its parent <svg>), offsetWidth/offsetHeight on HTMLElement.
+  // See resolveLayoutSize() for why a zero viewport is not merely inaccurate
+  // but actively breaks the in-bounds bump loop.
+  defineSizeGetter(element, 'clientWidth', 'width');
+  defineSizeGetter(element, 'clientHeight', 'height');
+  defineSizeGetter(window.HTMLElement?.prototype, 'offsetWidth', 'width');
+  defineSizeGetter(window.HTMLElement?.prototype, 'offsetHeight', 'height');
+
+  // JSDom's canvas has no 2D context (returns null and logs "Not
+  // implemented"). Provide a measurement-only context so text widths are
+  // non-zero and the noise is silenced.
+  if (canvas) {
+    const originalGetContext = canvas.getContext;
+    canvas.getContext = function (type, ...rest) {
+      if (type === '2d') {
+        return new FakeCanvasContext();
+      }
+      return originalGetContext
+        ? originalGetContext.call(this, type, ...rest)
+        : null;
+    };
+  }
+}

From 57cade9e02cae4ec991e35db0261ce400b27e107 Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Wed, 29 Jul 2026 14:17:34 -0700
Subject: [PATCH 10/13] test: Automatically glob and load Mocha test files when
 running in the browser

---
 .gitignore                                    |   3 +-
 .../blockly/scripts/gulpfiles/test_tasks.mjs  |  43 ++++++--
 packages/blockly/tests/mocha/index.html       | 101 +-----------------
 3 files changed, 35 insertions(+), 112 deletions(-)

diff --git a/.gitignore b/.gitignore
index f23a8695794..d5332699e27 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,9 +21,10 @@ packages/*/test/**/*.d.ts.map
 # Core
 packages/blockly/tests/compile/main_compressed.js
 packages/blockly/tests/compile/main_compressed.js.map
+packages/blockly/tests/mocha/test-modules.generated.mjs
 packages/blockly/temp/
 
-# Docs: 
+# Docs:
 # Autogenerated reference docs, do not check in
 packages/docs/docs/reference/
 packages/docs/.docusaurus
diff --git a/packages/blockly/scripts/gulpfiles/test_tasks.mjs b/packages/blockly/scripts/gulpfiles/test_tasks.mjs
index d32769bb89a..f7c5d1544a4 100644
--- a/packages/blockly/scripts/gulpfiles/test_tasks.mjs
+++ b/packages/blockly/scripts/gulpfiles/test_tasks.mjs
@@ -10,11 +10,12 @@
 /* eslint-env node */
 
 import asyncDone from 'async-done';
+import {spawnSync} from 'child_process';
+import * as fs from 'fs';
+import {globSync} from 'glob';
 import * as gulp from 'gulp';
 import gzip from 'gulp-gzip';
-import * as fs from 'fs';
 import * as path from 'path';
-import {spawnSync} from 'child_process';
 import {rimraf} from 'rimraf';
 
 import {RELEASE_DIR, TEST_TSC_OUTPUT_DIR} from './config.mjs';
@@ -263,6 +264,22 @@ async function metadata() {
   });
 }
 
+/**
+ * Generates tests/mocha/test-modules.generated.mjs,
+ * the list of tests imported by the browser harness (tests/mocha/index.html).
+ * Keeping it generated from a glob means new *_test.js files are picked up
+ * automatically and the browser and Node runners stay in sync.
+ * @return {Promise} Asynchronous result.
+ */
+function generateMochaIndex() {
+  return runTestTask('generateMochaIndex', async () => {
+    const files = globSync('**/*_test.js', {cwd: 'tests/mocha'}).sort();
+
+    const body = files.map((f) => `import './${f}';`).join('\n') + '\n';
+    fs.writeFileSync('tests/mocha/test-modules.generated.mjs', body);
+  });
+}
+
 /**
  * Run Mocha tests inside a browser.
  * @return {Promise} Asynchronous result.
@@ -277,16 +294,19 @@ function mocha() {
  * Run Mocha tests inside a browser and keep the browser open upon completion.
  * @return {Promise} Asynchronous result.
  */
-export function interactiveMocha() {
-  return runTestTask('interactiveMocha', () => {
-    return runMochaTestsInBrowser(false).then((result) => {
-      if (result) {
-        throw new Error('Mocha tests failed');
-      }
-      console.log('Mocha tests passed');
+export const interactiveMocha = gulp.series(
+  generateMochaIndex,
+  function interactiveMochaRun() {
+    return runTestTask('interactiveMocha', () => {
+      return runMochaTestsInBrowser(false).then((result) => {
+        if (result) {
+          throw new Error('Mocha tests failed');
+        }
+        console.log('Mocha tests passed');
+      });
     });
-  });
-}
+  },
+);
 
 /**
  * Helper method for comparison file.
@@ -417,6 +437,7 @@ const tasks = [
   // Build must run before the remaining tasks
   build,
   renamings,
+  generateMochaIndex,
   mocha,
   generators,
   node,
diff --git a/packages/blockly/tests/mocha/index.html b/packages/blockly/tests/mocha/index.html
index 9e1bafec77d..d5577bef835 100644
--- a/packages/blockly/tests/mocha/index.html
+++ b/packages/blockly/tests/mocha/index.html
@@ -291,106 +291,7 @@
       config.showDiff = false;
 
       // Import tests.
-      import './aria_test.js';
-      import './block_json_test.js';
-      import './block_test.js';
-      import './clipboard_test.js';
-      import './comment_test.js';
-      import './comment_deserialization_test.js';
-      import './connection_checker_test.js';
-      import './connection_db_test.js';
-      import './connection_test.js';
-      import './contextmenu_items_test.js';
-      import './contextmenu_test.js';
-      import './dialog_test.js';
-      import './dropdowndiv_test.js';
-      import './event_test.js';
-      import './event_block_change_test.js';
-      import './event_block_create_test.js';
-      import './event_block_delete_test.js';
-      import './event_block_drag_test.js';
-      import './dragger_test.js';
-      import './event_block_field_intermediate_change_test.js';
-      import './event_block_move_test.js';
-      import './event_bubble_open_test.js';
-      import './event_click_test.js';
-      import './event_comment_change_test.js';
-      import './event_comment_collapse_test.js';
-      import './event_comment_create_test.js';
-      import './event_comment_delete_test.js';
-      import './event_comment_move_test.js';
-      import './event_comment_drag_test.js';
-      import './event_comment_resize_test.js';
-      import './event_selected_test.js';
-      import './event_theme_change_test.js';
-      import './event_toolbox_item_select_test.js';
-      import './event_trashcan_open_test.js';
-      import './event_var_create_test.js';
-      import './event_var_delete_test.js';
-      import './event_var_rename_test.js';
-      import './event_var_type_change_test.js';
-      import './event_viewport_test.js';
-      import './extensions_test.js';
-      import './field_checkbox_test.js';
-      import './field_dropdown_test.js';
-      import './field_image_test.js';
-      import './field_label_serializable_test.js';
-      import './field_label_test.js';
-      import './field_number_test.js';
-      import './field_registry_test.js';
-      import './field_test.js';
-      import './field_textinput_test.js';
-      import './field_variable_test.js';
-      import './flyout_test.js';
-      import './focus_manager_test.js';
-      import './focusable_tree_traverser_test.js';
-      import './generator_test.js';
-      import './gesture_test.js';
-      import './icon_test.js';
-      import './input_test.js';
-      import './insertion_marker_test.js';
-      import './jso_deserialization_test.js';
-      import './jso_serialization_test.js';
-      import './json_test.js';
-      import './keyboard_movement_test.js';
-      import './keyboard_navigation_controller_test.js';
-      import './keyboard_navigation_test.js';
-      import './layering_test.js';
-      import './blocks/lists_test.js';
-      import './blocks/logic_ternary_test.js';
-      import './blocks/loops_test.js';
-      import './menu_item_test.js';
-      import './metrics_test.js';
-      import './mutator_test.js';
-      import './names_test.js';
-      import './navigation_test.js';
-      // TODO: Remove these tests.
-      import './old_workspace_comment_test.js';
-      import './procedure_map_test.js';
-      import './blocks/procedures_test.js';
-      import './rect_test.js';
-      import './registry_test.js';
-      import './render_management_test.js';
-      import './serializer_test.js';
-      import './shortcut_items_test.js';
-      import './shortcut_registry_test.js';
-      import './touch_test.js';
-      import './theme_test.js';
-      import './toast_test.js';
-      import './toolbox_test.js';
-      import './tooltip_test.js';
-      import './trashcan_test.js';
-      import './utils_test.js';
-      import './variable_map_test.js';
-      import './variable_model_test.js';
-      import './blocks/variables_test.js';
-      import './widget_div_test.js';
-      import './comment_view_test.js';
-      import './workspace_comment_test.js';
-      import './workspace_svg_test.js';
-      import './workspace_test.js';
-      import './xml_test.js';
-      import './zoom_controls_test.js';
+      import './test-modules.generated.mjs';
 
       window.__blocklyTestLoadState.markImportsComplete();
 

From 8327636acdfd514690192d46e8a1b87d77f9d823 Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Wed, 29 Jul 2026 14:29:53 -0700
Subject: [PATCH 11/13] test: Remove the old minimal Node smoketests

---
 .../blockly/scripts/gulpfiles/test_tasks.mjs  |   9 -
 packages/blockly/tests/node/.mocharc.js       |   6 -
 .../tests/node/node_modules/blockly-test      |   1 -
 packages/blockly/tests/node/run_node_test.mjs | 191 ------------------
 4 files changed, 207 deletions(-)
 delete mode 100644 packages/blockly/tests/node/.mocharc.js
 delete mode 120000 packages/blockly/tests/node/node_modules/blockly-test
 delete mode 100644 packages/blockly/tests/node/run_node_test.mjs

diff --git a/packages/blockly/scripts/gulpfiles/test_tasks.mjs b/packages/blockly/scripts/gulpfiles/test_tasks.mjs
index f7c5d1544a4..53af411477a 100644
--- a/packages/blockly/scripts/gulpfiles/test_tasks.mjs
+++ b/packages/blockly/scripts/gulpfiles/test_tasks.mjs
@@ -393,14 +393,6 @@ export async function generators() {
   });
 }
 
-/**
- * Run Node tests.
- * @return {Promise} Asynchronous result.
- */
-function node() {
-  return runTestCommand('node', 'mocha tests/node --config tests/node/.mocharc.js');
-}
-
 /**
  * Attempt advanced compilation of a Blockly app.
  * @returns {Promise} Async result.
@@ -440,7 +432,6 @@ const tasks = [
   generateMochaIndex,
   mocha,
   generators,
-  node,
   typeDefinitions,
   // Make sure these two are in series with each other
   advancedCompile,
diff --git a/packages/blockly/tests/node/.mocharc.js b/packages/blockly/tests/node/.mocharc.js
deleted file mode 100644
index 42378c7fa9d..00000000000
--- a/packages/blockly/tests/node/.mocharc.js
+++ /dev/null
@@ -1,6 +0,0 @@
-'use strict';
-
-module.exports = {
-  ui: 'tdd',
-  reporter: 'landing',
-};
diff --git a/packages/blockly/tests/node/node_modules/blockly-test b/packages/blockly/tests/node/node_modules/blockly-test
deleted file mode 120000
index 35f47bf7722..00000000000
--- a/packages/blockly/tests/node/node_modules/blockly-test
+++ /dev/null
@@ -1 +0,0 @@
-../../../dist
\ No newline at end of file
diff --git a/packages/blockly/tests/node/run_node_test.mjs b/packages/blockly/tests/node/run_node_test.mjs
deleted file mode 100644
index c6d21506987..00000000000
--- a/packages/blockly/tests/node/run_node_test.mjs
+++ /dev/null
@@ -1,191 +0,0 @@
-/**
- * @license
- * Copyright 2019 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-/** @fileoverview Mocha tests that test Blockly in Node. */
-
-console.log(process.cwd());
-
-// N.B. the file ./node_modules/blockly-test should be a symlink to
-// RELEASE_DIR (i.e. dist/) so that require will load the packaged
-// version of blockly as if it were an external dependency.
-//
-// Moreover, (as with the typescript tests) this link has to be
-// called something other than "blockly", because the node module
-// resolution will favour loading the nearest enclosing package
-// of the same name, which means that require('blockly') will load
-// based on the exports section of the package.json in the repository
-// root, but this fails because (at the time of writing) those paths
-// are relative to RELEASE_DIR (dist/, into which package.json is
-// copied when packaged), resulting in require() looking for the
-// compressed bundles in the wrong place.
-
-import * as Blockly from 'blockly-test';
-import {javascriptGenerator} from 'blockly-test/javascript';
-import {assert} from 'chai';
-
-const xmlText =
-  '<xml xmlns="https://developers.google.com/blockly/xml">\n' +
-  '  <block type="text_print" x="37" y="63">\n' +
-  '    <value name="TEXT">\n' +
-  '      <shadow type="text">\n' +
-  '        <field name="TEXT">Hello from Blockly!</field>\n' +
-  '      </shadow>\n' +
-  '    </value>\n' +
-  '  </block>\n' +
-  '</xml>';
-
-const json = {
-  'blocks': {
-    'languageVersion': 0,
-    'blocks': [
-      {
-        'type': 'procedures_defnoreturn',
-        'id': '0!;|f{%4H@mgQ`SIEDKV',
-        'x': 38,
-        'y': 163,
-        'icons': {
-          'comment': {
-            'text': 'Describe this function...',
-            'pinned': false,
-            'height': 80,
-            'width': 160,
-          },
-        },
-        'fields': {
-          'NAME': 'say hello',
-        },
-        'inputs': {
-          'STACK': {
-            'block': {
-              'type': 'text_print',
-              'id': 't^`WoL~R$t}rk]`JVFUP',
-              'inputs': {
-                'TEXT': {
-                  'shadow': {
-                    'type': 'text',
-                    'id': '_PxHV1tqEy60kP^].Qhh',
-                    'fields': {
-                      'TEXT': 'abc',
-                    },
-                  },
-                  'block': {
-                    'type': 'text_join',
-                    'id': 'K4.OZ9ql9j0f367238R@',
-                    'extraState': {
-                      'itemCount': 2,
-                    },
-                    'inputs': {
-                      'ADD0': {
-                        'block': {
-                          'type': 'text',
-                          'id': '5ElufS^j4;l:9N#|Yt$X',
-                          'fields': {
-                            'TEXT': 'The meaning of life is',
-                          },
-                        },
-                      },
-                      'ADD1': {
-                        'block': {
-                          'type': 'math_arithmetic',
-                          'id': ',QfcN`h]rQ86a]6J|di1',
-                          'fields': {
-                            'OP': 'MINUS',
-                          },
-                          'inputs': {
-                            'A': {
-                              'shadow': {
-                                'type': 'math_number',
-                                'id': 'ClcKUIPYleVQ_j7ZjK]^',
-                                'fields': {
-                                  'NUM': 44,
-                                },
-                              },
-                            },
-                            'B': {
-                              'shadow': {
-                                'type': 'math_number',
-                                'id': 'F_cU|uaP7oB-k(j~@X?g',
-                                'fields': {
-                                  'NUM': 2,
-                                },
-                              },
-                            },
-                          },
-                        },
-                      },
-                    },
-                  },
-                },
-              },
-            },
-          },
-        },
-      },
-      {
-        'type': 'procedures_callnoreturn',
-        'id': 'Ad^$sruQ.`6zNmQ6jPit',
-        'x': 38,
-        'y': 113,
-        'extraState': {
-          'name': 'say hello',
-        },
-      },
-    ],
-  },
-};
-
-suite('Test Node.js', function () {
-  test('Import XML', function () {
-    const xml = Blockly.utils.xml.textToDom(xmlText);
-
-    // Create workspace and import the XML
-    const workspace = new Blockly.Workspace();
-    Blockly.Xml.domToWorkspace(xml, workspace);
-  });
-  test('Roundtrip XML', function () {
-    const xml = Blockly.utils.xml.textToDom(xmlText);
-
-    const workspace = new Blockly.Workspace();
-    Blockly.Xml.domToWorkspace(xml, workspace);
-
-    const headlessXml = Blockly.Xml.workspaceToDom(workspace, true);
-    const headlessText = Blockly.Xml.domToPrettyText(headlessXml);
-
-    assert.equal(headlessText, xmlText, 'equal');
-  });
-  test('Generate Code', function () {
-    const xml = Blockly.utils.xml.textToDom(xmlText);
-
-    // Create workspace and import the XML
-    const workspace = new Blockly.Workspace();
-    Blockly.Xml.domToWorkspace(xml, workspace);
-
-    // Convert code
-    const code = javascriptGenerator.workspaceToCode(workspace);
-
-    // Check output
-    assert.equal("window.alert('Hello from Blockly!');", code.trim(), 'equal');
-  });
-  test('Import JSON', function () {
-    const workspace = new Blockly.Workspace();
-    Blockly.serialization.workspaces.load(json, workspace);
-  });
-  test('Roundtrip JSON', function () {
-    const workspace = new Blockly.Workspace();
-    Blockly.serialization.workspaces.load(json, workspace);
-
-    const jsonAfter = Blockly.serialization.workspaces.save(workspace);
-
-    assert.deepEqual(jsonAfter, json);
-  });
-  test('Dropdown getText works with no HTMLElement defined', function () {
-    const field = new Blockly.FieldDropdown([
-      ['firstOption', '1'],
-      ['secondOption', '2'],
-    ]);
-    assert.equal(field.getText(), 'firstOption');
-  });
-});

From 9bbfaec175f93a01f1a9e774cbef437f89b88a5e Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Wed, 29 Jul 2026 15:11:19 -0700
Subject: [PATCH 12/13] test: Use importmap instead of script tags to load Node
 modules

---
 packages/blockly/tests/mocha/index.html | 28 ++++++++++++-------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/packages/blockly/tests/mocha/index.html b/packages/blockly/tests/mocha/index.html
index d5577bef835..f6b5aa4400d 100644
--- a/packages/blockly/tests/mocha/index.html
+++ b/packages/blockly/tests/mocha/index.html
@@ -4,8 +4,6 @@
     <meta charset="utf-8" />
     <title>Mocha Tests for Blockly</title>
 
-    <link href="../../node_modules/mocha/mocha.css" rel="stylesheet" />
-
     <!-- Resolve the bare/subpath specifiers used by the test modules so the
          same import statements work in both the browser and under Node. The
          "#core/" and "#generators/" prefixes mirror the "imports" field in
@@ -14,6 +12,9 @@
       {
         "imports": {
           "chai": "../../node_modules/chai/index.js",
+          "mocha": "../../node_modules/mocha/mocha.js",
+          "mocha/": "../../node_modules/mocha/",
+          "sinon": "../../node_modules/sinon/pkg/sinon-esm.js",
           "#core/": "../../build/src/core/",
           "#generators/": "../../build/src/generators/"
         }
@@ -153,17 +154,6 @@
       </g>
       <g id="nonTreeGroupForEphemeralFocus"></g>
     </svg>
-    <!-- Load mocha et al. before Blockly and the test modules so that
-         we can safely import the test modules that make calls
-         to (e.g.)  suite() at the top level. -->
-    <script src="../../node_modules/mocha/mocha.js"></script>
-    <script src="../../node_modules/sinon/pkg/sinon.js"></script>
-    <script>
-      mocha.setup({
-        ui: 'tdd',
-        failZero: true,
-      });
-    </script>
     <script>
       (function () {
         const failureDiv = document.getElementById('failureCount');
@@ -288,10 +278,20 @@
       import '../../build/blocks.loader.mjs';
       import {javascriptGenerator} from '../../build/javascript.loader.mjs';
       import {config} from 'chai';
+      import 'mocha';
+      import mochaStyles from 'mocha/mocha.css' with {type: 'css'};
+      import sinon from 'sinon';
+
       config.showDiff = false;
+      globalThis.sinon = sinon;
+      document.adoptedStyleSheets.push(mochaStyles);
+      mocha.setup({
+        ui: 'tdd',
+        failZero: true,
+      });
 
       // Import tests.
-      import './test-modules.generated.mjs';
+      await import('./test-modules.generated.mjs');
 
       window.__blocklyTestLoadState.markImportsComplete();
 

From cebc4f1adda2e1d77c8da6fcc548128b65adf99c Mon Sep 17 00:00:00 2001
From: Aaron Dodson <aaron.dodson@raspberrypi.org>
Date: Wed, 29 Jul 2026 15:19:12 -0700
Subject: [PATCH 13/13] test: Use dom_fixtures.js as single source of truth for
 test markup

---
 packages/blockly/tests/mocha/index.html | 180 +-----------------------
 1 file changed, 7 insertions(+), 173 deletions(-)

diff --git a/packages/blockly/tests/mocha/index.html b/packages/blockly/tests/mocha/index.html
index f6b5aa4400d..bc77544301c 100644
--- a/packages/blockly/tests/mocha/index.html
+++ b/packages/blockly/tests/mocha/index.html
@@ -55,105 +55,6 @@
     <div id="failureCount" style="display: none" tests_failed="unset"></div>
     <div id="failureMessages" style="display: none"></div>
     <div id="loadStatus" data-status="pending" style="display: none"></div>
-    <div id="testFocusableTree1">
-      Focusable tree 1
-      <div id="testFocusableTree1.node1" style="margin-left: 1em">
-        Tree 1 node 1
-        <div id="testFocusableTree1.node1.child1" style="margin-left: 2em">
-          Tree 1 node 1 child 1
-          <div
-            id="testFocusableTree1.node1.child1.unregisteredChild1"
-            style="margin-left: 3em">
-            Tree 1 node 1 child 1 child 1 (unregistered)
-          </div>
-        </div>
-      </div>
-      <div id="testFocusableTree1.node2" style="margin-left: 1em">
-        Tree 1 node 2
-        <div
-          id="testFocusableTree1.node2.unregisteredChild1"
-          style="margin-left: 2em">
-          Tree 1 node 2 child 2 (unregistered)
-        </div>
-      </div>
-      <div id="testFocusableTree1.unregisteredChild1" style="margin-left: 1em">
-        Tree 1 child 1 (unregistered)
-      </div>
-    </div>
-    <div id="testFocusableTree2">
-      Focusable tree 2
-      <div id="testFocusableTree2.node1" style="margin-left: 1em">
-        Tree 2 node 1
-        <div id="testFocusableNestedTree4" style="margin-left: 2em">
-          Nested tree 4
-          <div id="testFocusableNestedTree4.node1" style="margin-left: 3em">
-            Tree 4 node 1 (nested)
-            <div
-              id="testFocusableNestedTree4.node1.unregisteredChild1"
-              style="margin-left: 4em">
-              Tree 4 node 1 child 1 (unregistered)
-            </div>
-          </div>
-        </div>
-      </div>
-      <div id="testFocusableNestedTree5" style="margin-left: 1em">
-        Nested tree 5
-        <div id="testFocusableNestedTree5.node1" style="margin-left: 2em">
-          Tree 5 node 1 (nested)
-        </div>
-      </div>
-    </div>
-    <div id="testUnregisteredFocusableTree3">
-      Unregistered tree 3
-      <div id="testUnregisteredFocusableTree3.node1" style="margin-left: 1em">
-        Tree 3 node 1 (unregistered)
-      </div>
-    </div>
-    <div id="testUnfocusableElement">Unfocusable element</div>
-    <div id="nonTreeElementForEphemeralFocus" />
-    <svg width="250" height="250">
-      <g id="testFocusableGroup1">
-        <g id="testFocusableGroup1.node1">
-          <rect x="0" y="0" width="250" height="30" fill="grey" />
-          <text x="10" y="20" class="svgText">Group 1 node 1</text>
-          <g id="testFocusableGroup1.node1.child1">
-            <rect x="0" y="30" width="250" height="30" fill="lightgrey" />
-            <text x="10" y="50" class="svgText">Tree 1 node 1 child 1</text>
-          </g>
-        </g>
-        <g id="testFocusableGroup1.node2">
-          <rect x="0" y="60" width="250" height="30" fill="grey" />
-          <text x="10" y="80" class="svgText">Group 1 node 2</text>
-          <g id="testFocusableGroup1.node2.unregisteredChild1">
-            <rect x="0" y="90" width="250" height="30" fill="lightgrey" />
-            <text x="10" y="110" class="svgText">
-              Tree 1 node 2 child 2 (unregistered)
-            </text>
-          </g>
-        </g>
-      </g>
-      <g id="testFocusableGroup2">
-        <g id="testFocusableGroup2.node1">
-          <rect x="0" y="120" width="250" height="30" fill="grey" />
-          <text x="10" y="140" class="svgText">Group 2 node 1</text>
-        </g>
-        <g id="testFocusableNestedGroup4">
-          <g id="testFocusableNestedGroup4.node1">
-            <rect x="0" y="150" width="250" height="30" fill="lightgrey" />
-            <text x="10" y="170" class="svgText">Group 4 node 1 (nested)</text>
-          </g>
-        </g>
-      </g>
-      <g id="testUnregisteredFocusableGroup3">
-        <g id="testUnregisteredFocusableGroup3.node1">
-          <rect x="0" y="180" width="250" height="30" fill="grey" />
-          <text x="10" y="200" class="svgText">
-            Tree 3 node 1 (unregistered)
-          </text>
-        </g>
-      </g>
-      <g id="nonTreeGroupForEphemeralFocus"></g>
-    </svg>
     <script>
       (function () {
         const failureDiv = document.getElementById('failureCount');
@@ -281,10 +182,17 @@
       import 'mocha';
       import mochaStyles from 'mocha/mocha.css' with {type: 'css'};
       import sinon from 'sinon';
+      import {installFixtures} from './test_helpers/dom_fixtures.js';
 
       config.showDiff = false;
       globalThis.sinon = sinon;
       document.adoptedStyleSheets.push(mochaStyles);
+
+      // The focusable trees, toolbox definitions and #blocklyDiv the tests
+      // expect. Shared with the Node harness so both run against identical
+      // markup.
+      installFixtures();
+
       mocha.setup({
         ui: 'tdd',
         failZero: true,
@@ -348,79 +256,5 @@
         window.__blocklyTestLoadState.reportFailure(error);
       }
     </script>
-
-    <div id="blocklyDiv"></div>
-
-    <xml
-      xmlns="https://developers.google.com/blockly/xml"
-      id="toolbox-simple"
-      style="display: none">
-      <block type="logic_compare">
-        <field name="OP">NEQ</field>
-        <value name="A">
-          <shadow type="math_number">
-            <field name="NUM">1</field>
-          </shadow>
-        </value>
-        <value name="B">
-          <block type="math_number">
-            <field name="NUM">2</field>
-          </block>
-        </value>
-      </block>
-      <sep gap="20"></sep>
-      <button text="insert" callbackkey="insertConnectionRows"></button>
-      <label text="tooltips"></label>
-    </xml>
-
-    <xml
-      xmlns="https://developers.google.com/blockly/xml"
-      id="toolbox-categories"
-      style="display: none">
-      <category name="First" css-container="something">
-        <block type="basic_block">
-          <field name="TEXT">FirstCategory-FirstBlock</field>
-        </block>
-        <block type="basic_block">
-          <field name="TEXT">FirstCategory-SecondBlock</field>
-        </block>
-      </category>
-      <category name="Second">
-        <block type="basic_block">
-          <field name="TEXT">SecondCategory-FirstBlock</field>
-        </block>
-      </category>
-    </xml>
-
-    <xml
-      xmlns="https://developers.google.com/blockly/xml"
-      id="toolbox-test"
-      style="display: none">
-      <category name="First" expanded="true" categorystyle="logic_category">
-        <sep gap="-1"></sep>
-        <button text="insert" callbackkey="insertConnectionRows"></button>
-        <block type="stack_block"></block>
-        <block type="stack_block"></block>
-      </category>
-      <category name="Second">
-        <block type="stack_block"></block>
-      </category>
-      <sep toolboxitemid="separator" gap="-1"></sep>
-      <category name="Variables" custom="VARIABLE"></category>
-      <category name="NestedCategory">
-        <category toolboxitemid="nestedCategory" name="NestedItemOne">
-          <block type="stack_block"></block>
-        </category>
-        <block type="stack_block"></block>
-      </category>
-      <category name="lastItem"></category>
-    </xml>
-
-    <xml
-      xmlns="https://developers.google.com/blockly/xml"
-      id="gesture-test-toolbox"
-      style="display: none">
-      <block type="test_field_block"></block>
-    </xml>
   </body>
 </html>