[Pedro Henrique Penna (ppenna)]

#952 changed how the summarize job of nvx-rs-mutants.yml finds the shards' outcomes:

• Each shard uploads its outcomes under its index.
• The download merges every shard's artifact into shards/.
• The merge counts a shard as reported when shards/<index>/outcomes.json exists.
• The merge step fails before it merges anything when the mutants job did not succeed, which it reads from MUTANTS_RESULT under set -u.

MutantsWorkflowStepTests in scripts/test_nvx_rs_mutants.py still ran the merge step with the old layout, one directory named after each artifact, and without MUTANTS_RESULT. On Linux, where these tests run (they skip on Windows), two of them fail on dev:

• test_the_outcomes_of_every_shard_merge: /usr/bin/bash: line 2: MUTANTS_RESULT: unbound variable
• test_shards_that_report_nothing_fail_the_merge: '::error::Only 1 of 3 shards reported' not found in ''

So NVX CLI / Linux fails for every pull request based on dev, as in run 40958853538 of #1021.

Changes

• scripts: test the mutants merge against the shards' indexed outcomes: the tests lay the outcomes out as the download does, under each shard's index and with outcomes.json, and pass the mutants job's result. The test of missing shards also gives one shard lists without outcomes.json, which the merge must leave out of both the lists and the count. A new test requires that a mutants job that failed, was cancelled, or was skipped fail the merge before it merges or summarizes anything.

The workflow itself is unchanged.

Validation

• On the nvx-kvm-test Linux VM, the two tests fail at b558d34bd, which merged ci: fix nvx-rs mutants summarize miscounting shards #952, and pass at its parent, 29c68547b.
• At this branch's head, all 11 tests of scripts/test_nvx_rs_mutants.py pass there, and so does the whole validate-nvx unittest list: 1,484 tests, 34 skipped.
• Locally on Windows: ruff check, ruff format --check, and pyright --pythonplatform Linux and Windows are clean, and the module's Windows tests pass.

[Copilot]

🟢 Approval recommended

The mutation-workflow test updates have no active review issues.

No open issues 🎉

What changed in this PR

Updates the mutation-workflow tests to match the indexed shard layout introduced in #952, fixing stale test assumptions without changing the workflow itself.

Changes:

• Stages shard fixtures under their indexes with outcomes.json and supplies MUTANTS_RESULT.
• Verifies that shards without outcomes.json are excluded from merged lists and the reported count.
• Adds coverage ensuring failed, cancelled, or skipped mutants jobs stop before merging or summarizing.

File	Description
scripts/​test_nvx_rs_mutants.py	Aligns merge fixtures with the workflow and strengthens missing-shard and unsuccessful-job checks.

_{Review effort: Balanced}