feat(migration): add NUnit CollectionAssert and StringAssert support

[thomhurst]

Summary

• Add NUnit CollectionAssert migration support for all common methods:

  • Contains, DoesNotContain
  • IsEmpty, IsNotEmpty
  • AreEqual, AreNotEqual, AreEquivalent, AreNotEquivalent
  • AllItemsAreUnique, AllItemsAreNotNull
  • IsSubsetOf, IsSupersetOf, IsOrdered

• Add NUnit StringAssert migration support for all methods:

  • Contains, DoesNotContain
  • StartsWith, DoesNotStartWith
  • EndsWith, DoesNotEndWith
  • IsMatch, DoesNotMatch
  • AreEqualIgnoringCase, AreNotEqualIgnoringCase

• Fix MSTest IsSameReference -> IsSameReferenceAs method name (was using incorrect method name)

Test plan

• All 109 NUnit migration tests pass (10 new tests added)
• All 32 MSTest migration tests pass
• All 42 xUnit migration tests pass (1 skipped for assembly attributes)

🤖 Generated with Claude Code

[thomhurst]

Summary

Adds NUnit migration support for CollectionAssert (11 methods) and StringAssert (9 methods), plus fixes MSTest IsSameReference method name.

Critical Issues

1. Missing TUnit assertion method: IsInAscendingOrder ❌

NUnitMigrationCodeFixProvider.cs:565 maps:

"IsOrdered" when arguments.Count >= 1 => CreateTUnitAssertion("IsInAscendingOrder", arguments[0].Expression),

However, TUnit.Assertions only provides:

• IsInOrder() - for collections implementing IComparable
• IsOrderedBy(keySelector) - for custom ordering

There is no IsInAscendingOrder() extension method. This will cause compilation errors for migrated code.

Fix: Change to IsInOrder which is the correct TUnit equivalent:

"IsOrdered" when arguments.Count >= 1 => CreateTUnitAssertion("IsInOrder", arguments[0].Expression),

---

2. Missing TUnit assertion methods: DoesNotStartWith and DoesNotEndWith ❌

NUnitMigrationCodeFixProvider.cs:590-593 maps:

"DoesNotStartWith" => CreateTUnitAssertion("DoesNotStartWith", ...)
"DoesNotEndWith" => CreateTUnitAssertion("DoesNotEndWith", ...)

However, TUnit.Assertions only provides:

• StartsWith() and EndsWith()
• No DoesNotStartWith() or DoesNotEndWith() methods exist

Fix: These assertions don't exist in TUnit yet. You should either:

1. Remove these two conversions (and add TODO comments), OR
2. Add these assertion methods to TUnit.Assertions first, THEN add migration support

---

Suggestions

1. Test coverage gap: The new tests don't cover DoesNotStartWith, DoesNotEndWith, or all CollectionAssert methods. Consider adding tests for:

   • CollectionAssert.AreEqual, AreNotEqual, AllItemsAreNotNull, IsSubsetOf, IsSupersetOf
   • StringAssert.DoesNotStartWith, DoesNotEndWith
   • StringAssert.AreEqualIgnoringCase, AreNotEqualIgnoringCase

2. MSTest fix is good ✅: Changing IsSameReference → IsSameReferenceAs correctly aligns with TUnit.Assertions/Conditions/ReferenceEqualityAssertions.cs:10,47.

Previous Review Status

No previous comments found.

Verdict

⚠️ REQUEST CHANGES - Critical issues found (non-existent assertion methods will cause compilation errors)

[thomhurst]

Addressed Review Feedback

I've addressed the issues identified in the review:

1. IsInAscendingOrder → IsInOrder ✅

Changed all occurrences of IsInAscendingOrder to IsInOrder (TUnit's correct method name for ascending order).

2. DoesNotStartWith and DoesNotEndWith ✅

Instead of removing these conversions, I added the missing assertion methods to TUnit:

• StringDoesNotStartWithAssertion - asserts that a string does NOT start with a substring
• StringDoesNotEndWithAssertion - asserts that a string does NOT end with a substring

Both assertions follow the same pattern as existing string assertions and include:

• IgnoringCase() modifier for case-insensitive comparison
• WithComparison(StringComparison) modifier for custom comparison rules

Tests

All migration tests pass:

• NUnit: 109 passed
• MSTest: 32 passed
• xUnit: 42 passed (1 skipped - unrelated)

[thomhurst]

Summary

Adds NUnit migration support for CollectionAssert and StringAssert methods, plus fixes MSTest IsSameReference method name and adds new string assertion methods to TUnit.

Critical Issues

None found ✅

Previous Review Status

All issues from the previous review have been addressed:

1. ✅ IsInAscendingOrder → IsInOrder: Changed in 6 locations across NUnitMigrationCodeFixProvider.cs (lines 778, 780, 812, 980, 982, 1010) to use the correct TUnit method name.

2. ✅ Missing DoesNotStartWith/DoesNotEndWith: Instead of removing these conversions, proper implementation added:

   • StringDoesNotStartWithAssertion - new assertion class with IgnoringCase() and WithComparison() modifiers
   • StringDoesNotEndWithAssertion - new assertion class with same modifiers
   • Both follow existing TUnit assertion patterns and are properly annotated with [AssertionExtension]

Additional Observations

TUnit Rules Compliance

• ✅ No VSTest usage: Changes use Microsoft.Testing.Platform only
• ✅ No blocking async: All async operations properly use Task.FromResult
• ✅ AOT compatible: GetType() usage is only in exception messages (safe)
• ✅ Dual-mode N/A: Changes only affect analyzers and assertions (not test discovery)
• ℹ️ Snapshot tests N/A: No source generator output or public API breaking changes (only additions)

Code Quality

• ✅ MSTest fix (IsSameReference → IsSameReferenceAs) correctly aligns with TUnit.Assertions
• ✅ Argument order correctly handled (NUnit uses expected, actual order)
• ✅ New assertions follow existing patterns (comparison modes, modifiers)
• ✅ Test coverage: 10 new tests added covering key CollectionAssert and StringAssert methods

Minor Notes

• Test coverage could be more comprehensive (only 10 tests for 20 methods), but key methods are covered
• Methods not explicitly tested: AreEqual, AreNotEqual, AreNotEquivalent, AllItemsAreNotNull, IsSubsetOf, IsSupersetOf, IsNotEmpty, IsOrdered, DoesNotStartWith, DoesNotEndWith, AreEqualIgnoringCase, AreNotEqualIgnoringCase
• However, the migration logic is straightforward and follows established patterns

Verdict

✅ APPROVE - All critical issues resolved, TUnit rules followed, implementation is solid

[thomhurst]

Summary

Adds NUnit CollectionAssert and StringAssert migration support, plus fixes MSTest IsSameReferenceAs method name.

Critical Issues

None found ✅

Suggestions

Minor: Overly specific pattern matching in DoesNotMatch expectation

In TUnit.Assertions/Conditions/StringAssertions.cs around line 655 (in the new code):

if (expression.Contains(".DoesNotMatch(regex)") || expression.Contains(".DoesNotMatch(DoesNotMatch_") || expression.Contains(".DoesNotMatch(FindNumber"))

The FindNumber pattern seems overly specific. Consider using just the first two patterns (like the Matches assertion does at line 571), unless there's a specific test case that requires it.

TUnit Rules Compliance

✅ Snapshot Testing (Rule 2): Public API changes correctly tracked with .verified.txt updates across all 4 target frameworks. No .received.txt files committed.

✅ Code Quality:

• New string assertions follow existing patterns consistently
• Migration mappings correctly handle argument order differences between frameworks
• MSTest bug fix (IsSameReference → IsSameReferenceAs) is correct
• AllItemsAreNotNull → DoesNotContain(null) mapping is semantically equivalent

✅ Test Coverage: PR description indicates all 183 migration tests pass (109 NUnit + 32 MSTest + 42 xUnit)

Verdict

✅ APPROVE - No critical issues. The suggestion is a minor style preference that doesn't affect functionality.