[test-improver] test: add edge case tests for IgnoreStringMethodReturnValueAnalyzer

[Evangelink]

Goal and Rationale

IgnoreStringMethodReturnValueAnalyzer (MSTEST0055) had only 5 tests, all covering the happy path (diagnostic fires / doesn't fire based on whether the result of Contains, StartsWith, or EndsWith is used). Three distinct code paths in the analyzer's guard logic were completely untested:

Untested path	Guard
Discard assignment _ = str.Contains(...)	expressionStatementOperation.Operation is not IInvocationOperation early return
String method call inside a lambda block body	ExpressionStatement inside lambda — should still fire
String method result used as a receiver in a chained call	IsStringMethodCall on the outer call (not a string method) — should not fire

Approach

Added three [TestMethod] entries to IgnoreStringMethodReturnValueAnalyzerTests.cs:

Test	What it covers
WhenDiscardAssignmentIgnoresReturnValue_NoDiagnostic	_ = str.Contains("Hello") → outer operation is IAssignmentOperation, not IInvocationOperation → early return, no diagnostic
WhenStringMethodReturnValueIgnoredInsideLambda_Diagnostic	() => { str.Contains("Hello"); } → ExpressionStatement inside lambda body triggers diagnostic
WhenStringMethodResultUsedAsReceiverForChainedCall_NoDiagnostic	str.Contains("Hello").GetHashCode() → outermost ExpressionStatement operation is GetHashCode() on System.Boolean, not a string method → no diagnostic on Contains

Trade-offs

Purely additive — no production code changes, no new dependencies.

Test Status

All 8 tests pass (5 existing + 3 new):

Test run summary: Passed!
  total: 8
  failed: 0
  succeeded: 8
  duration: 5s 537ms

Reproducibility

.dotnet/dotnet run --project test/UnitTests/MSTest.Analyzers.UnitTests/ -f net8.0 --no-build -- \
  --filter "FullyQualifiedName~IgnoreStringMethodReturnValueAnalyzerTests"

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Pull request overview

Adds additional unit-test coverage for the MSTest analyzer IgnoreStringMethodReturnValueAnalyzer (MSTEST0055) to cover previously untested guard/shape scenarios, without changing production analyzer behavior.

Changes:

• Added a test ensuring discard assignments (_ = str.Contains(...)) do not produce MSTEST0055 diagnostics.
• Added a test ensuring ignored string-method return values inside a lambda block body do produce diagnostics.
• Added a test ensuring chained calls where the string method result is used as a receiver (e.g. str.Contains(...).GetHashCode()) do not produce diagnostics.

Show a summary per file

File	Description
test/UnitTests/MSTest.Analyzers.UnitTests/IgnoreStringMethodReturnValueAnalyzerTests.cs	Adds three new test cases covering discard assignment, lambda-body expression statements, and chained-call receiver usage scenarios for MSTEST0055.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Low