Bug: efcdatamodel-success-path-test-uses-incidental-crash-as-barrier #699

• Work Mode: full-bug

Summary

MoveToFolderAsync_WhenArchiveRootResolves_StillReadsItOnce terminates its success path on a
NullReferenceException raised by the EmailFiler collaborator rather than on a deliberate stopping
point. The test is correct today, but its failure message would misdirect a future maintainer if
EmailFiler.SortAsync ever gains a null guard.

Environment

• OS/version: Windows 11, .NET Framework 4.8.1
• Python version: not applicable; this is an MSTest C# unit test
• Command/flags used: vstest.console.exe QuickFiler.Test\bin\Debug\QuickFiler.Test.dll /TestCaseFilter:"FullyQualifiedName~EfcDataModelArchiveRootTests"
• Data source or fixture: TestableEfcDataModel with a strict Mock<IOlObjects> and a parameterless MailItemHelper

Steps to Reproduce

1. Add a null guard to EmailFiler.SortAsync so it returns false instead of dereferencing a null FolderInfo.
2. Re-run MoveToFolderAsync_WhenArchiveRootResolves_StillReadsItOnce.

Expected Behavior

The test terminates the success path deliberately and asserts only the invariant it exists to pin,
which is olObjects.VerifyGet(value => value.ArchiveRootPath, Times.Once()). A failure reports a
problem with the archive-root read count.

Actual Behavior

The test asserts await act.Should().ThrowAsync<NullReferenceException>() before the VerifyGet. That
exception is not a property of the unit under test: it is the EmailFiler collaborator dereferencing
a MailItemHelper whose folder information is null, several frames past the code issue 638 touched.
Once EmailFiler no longer throws there, the test fails with a message about a missing
NullReferenceException and points at the wrong subsystem.

Logs / Screenshots

• Attached minimal logs or screenshot
• Snippet: not captured; the condition is latent and does not reproduce against the current tree.

Impact / Severity

• Blocker
• High
• Medium
• Low

Source

From: docs/features/potential/2026-08-29-efcdatamodel-success-path-test-uses-incidental-crash-as-barrier.md