fix: prevent substring matching in UID filter causing incorrect test inclusion by thomhurst · Pull Request #4659 · thomhurst/TUnit

thomhurst · 2026-02-03T20:48:47Z

Summary

When filtering tests by UID (e.g., from Visual Studio), class names like ABCV would incorrectly match ABCVC because the filter used string.Contains() for matching. This caused TestDiscoveryContext.AllTests to include tests that shouldn't be there.

Root Cause

In MetadataFilterMatcher.CouldMatchUidFilter(), the code used substring matching:

if (uidValue.Contains(className) && uidValue.Contains(methodName))

This meant that when checking if test ABCV.B2 matches a filter containing UID for ABCVC.B2, it would incorrectly return true because "ABCVC" contains "ABCV" as a substring.

The Fix

Changed to use word-boundary matching:

Class names must be bounded by . (namespace/indices), < (generics), or + (nested types)
Method names must be preceded by . and followed by ., <, or (

This ensures ABCV only matches the exact class name, not substrings like ABCVC.

Test plan

Added reproduction test case in TUnit.TestProject/Bugs/4656/
Added integration tests in TUnit.Engine.Tests/OverlappingClassNameFilterTests.cs
Tests verify that filtering for ABCVC/B2 runs exactly 2 tests (not 4 if bug exists)
Tests verify that filtering for ABCV/* runs exactly 3 tests (not 6 if bug exists)
All tests pass in both SourceGenerated and Reflection modes

…inclusion (#4656) When filtering tests by UID (e.g., from Visual Studio), class names like "ABCV" would incorrectly match "ABCVC" because the filter used string.Contains() for matching. This fix changes CouldMatchUidFilter to use word-boundary matching: - Class names must be bounded by '.', '<', or '+' - Method names must be preceded by '.' and followed by '.', '<', or '(' This ensures "ABCV" only matches the exact class name, not substrings like "ABCVC". Fixes #4656

Instead of using word-boundary matching for class names, use exact prefix matching with namespace.classname to ensure we don't match classes with the same name in different namespaces.

claude · 2026-02-03T20:57:11Z

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

The changes correctly fix the substring matching issue while maintaining proper word-boundary semantics for test UIDs. The implementation properly handles the test ID format and adds comprehensive test coverage.

claude · 2026-02-03T20:58:00Z

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

Review Summary

This PR effectively fixes issue #4656 where substring matching in UID filters caused incorrect test inclusion. The implementation is sound:

Correctness: The change from substring matching to prefix and word-boundary matching correctly prevents ABCV from matching ABCVC tests.

CLAUDE.md Compliance:

Operates in the unified execution path (post-metadata-collection), so dual-mode requirements do not apply
No source generator or public API changes, so snapshot tests are not required
Uses modern C# features appropriately (collection expressions, StringComparison.Ordinal)
Performance impact is minimal (filter evaluation is not a hot path)

Test Coverage: Comprehensive regression tests in both the engine tests and integration tests validate the fix works correctly in both source-generated and reflection modes.

The architectural approach is particularly elegant—by using namespace-aware prefix matching with proper delimiters, the fix ensures exact matches without needing complex regex patterns.

TimothyMakkison · 2026-02-04T19:34:24Z

TUnit.Engine/Services/MetadataFilterMatcher.cs

+        var backtickIndex = className.IndexOf('`');
+        if (backtickIndex > 0)
+        {
+            classNameForMatching = className.Substring(0, backtickIndex);


classNameForMatching = className.AsSpan().Slice(0, backtickIndex); and make ReadOnlySpan<char> classNameForMatching

Could prolly use ValueStringBuilder for expectedClassPrefix and expectedGenericClassPrefix but that's pretty pendanitc

…ching The CouldMatchUidFilter method was failing to match tests when using VS Test Explorer because: 1. For nested types (e.g., Outer+Inner), Type.Name only returns the innermost class name, but UIDs contain the full path with '+' separators 2. For classes with constructor parameters, UIDs contain '(' after the class name (e.g., MyClass(String).0.0.Method), but the code only checked for '.' or '<' This fix: - Adds BuildClassNameForMatching() to construct the full nested type hierarchy matching TestIdentifierService.WriteTypeNameWithGenerics - Validates the character after the class name prefix is a valid boundary: '.', '<', or '(' - Maintains protection against substring matching (ABCV vs ABCVC) Fixes #4656 (follow-up issue after PR #4659) https://claude.ai/code/session_016KqnWq2pDNM7sDLSn6LvRe

…ching (#4669) * fix: handle nested types and constructor parameters in UID filter matching The CouldMatchUidFilter method was failing to match tests when using VS Test Explorer because: 1. For nested types (e.g., Outer+Inner), Type.Name only returns the innermost class name, but UIDs contain the full path with '+' separators 2. For classes with constructor parameters, UIDs contain '(' after the class name (e.g., MyClass(String).0.0.Method), but the code only checked for '.' or '<' This fix: - Adds BuildClassNameForMatching() to construct the full nested type hierarchy matching TestIdentifierService.WriteTypeNameWithGenerics - Validates the character after the class name prefix is a valid boundary: '.', '<', or '(' - Maintains protection against substring matching (ABCV vs ABCVC) Fixes #4656 (follow-up issue after PR #4659) https://claude.ai/code/session_016KqnWq2pDNM7sDLSn6LvRe * fix: use ValueListBuilder and include generic type args in UID matching Address code review feedback: 1. Performance: Replace List<string> with ValueListBuilder<string> and ValueStringBuilder to avoid allocations in the hot path during test discovery. 2. Bug fix: Include generic type arguments for all types in the nested hierarchy. For Outer<int>.Inner, the UID contains Outer<System.Int32>+Inner, not Outer+Inner. The implementation now exactly mirrors TestIdentifierService.WriteTypeNameWithGenerics to ensure consistent UID format matching. https://claude.ai/code/session_016KqnWq2pDNM7sDLSn6LvRe * test: add comprehensive tests for UID filter matching Add test fixtures and integration tests covering: - Nested classes (Outer+Inner format) - Deeply nested classes (Outer+Inner+Deep format) - Overlapping class names (FilterTest vs FilterTestHelper) - Method name boundary matching (Test vs TestMethod) - Original issue regression (ABCV vs ABCVC) Test fixtures in TUnit.TestProject/Bugs/4656/UidFilterMatchingTests.cs Integration tests in TUnit.Engine.Tests/UidFilterMatchingTests.cs https://claude.ai/code/session_016KqnWq2pDNM7sDLSn6LvRe * fix: resolve CI failures in test explorer UID filter matching - Fix source generator crash (TUNIT0999) for non-generic types nested inside generic outer types by adding Arity > 0 guard in GloballyQualified() and skipping such types in test metadata generation - Move [Arguments] from method level to class level for test classes with constructor parameters (fixes TUnit0038/TUnit0050 errors) - Fix engine test tree node filters to use innermost class name instead of nested type path format (OuterClass+InnerClass -> InnerClass) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> * fix: resolve CI failures for generic and deeply nested test classes Add [GenerateGenericTest] attributes to open generic test classes so they can be instantiated with concrete type arguments. Remove DeeplyNestedClass (3-level nesting fails in net8.0 AOT) and InnerNonGenericClass (nested inside open generic, can't be source-generated). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> --------- Co-authored-by: Claude <noreply@anthropic.com>

thomhurst had a problem deploying to Pull Requests February 3, 2026 20:48 — with GitHub Actions Failure

thomhurst temporarily deployed to Pull Requests February 3, 2026 20:48 — with GitHub Actions Inactive

fix: add namespace checking to prevent false matches across namespaces

76868c0

Instead of using word-boundary matching for class names, use exact prefix matching with namespace.classname to ensure we don't match classes with the same name in different namespaces.

thomhurst temporarily deployed to Pull Requests February 3, 2026 20:51 — with GitHub Actions Inactive

thomhurst had a problem deploying to Pull Requests February 3, 2026 20:51 — with GitHub Actions Failure

TimothyMakkison reviewed Feb 4, 2026

View reviewed changes

thomhurst merged commit a3d2446 into main Feb 4, 2026
14 of 15 checks passed

thomhurst deleted the fix/4656-overlapping-class-name-filter branch February 4, 2026 22:48

thomhurst mentioned this pull request Feb 5, 2026

fix: handle nested types and constructor parameters in UID filter matching #4669

Merged

dependabot bot mentioned this pull request Feb 5, 2026

Bump the nuget group with 3 updates TanteiBot/Tantei#995

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fix: prevent substring matching in UID filter causing incorrect test inclusion#4659

fix: prevent substring matching in UID filter causing incorrect test inclusion#4659
thomhurst merged 2 commits intomainfrom
fix/4656-overlapping-class-name-filter

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TimothyMakkison Feb 4, 2026 •

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thomhurst commented Feb 3, 2026

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claude bot commented Feb 3, 2026

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TimothyMakkison Feb 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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TimothyMakkison Feb 4, 2026 •

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