Fix MSTest fixture method fixers removing comments from method bodies

[Copilot]

Issue

The MSTest fixture method code fixers (MSTest0001, MSTest0002, MSTest0006, MSTest0007, MSTest0008, MSTest0009) were incorrectly removing comments from method bodies when applying fixes. This was most noticeable with MSTest0008 (TestInitialize) as reported in the issue.

For example, when fixing a TestInitialize method signature:

[TestInitialize]
public void TestSetup(TestContext tc)
{
    SomeCode();

    // Some comments;
}

The fixer would remove the parameter but also remove the comment, producing:

[TestInitialize]
public void TestSetup()
{
    SomeCode();
}

Root Cause

The FixtureMethodFixer helper class was using SyntaxGenerator.MethodDeclaration() to create a completely new method from scratch. This approach extracted only the executable statements from the original method using GetStatements(), which discarded all trivia including comments, whitespace, and formatting.

Solution

Modified FixtureMethodFixer.cs to use Roslyn's .WithXXX() pattern for incremental syntax transformations. Instead of creating a new method, the fixer now:

1. Starts with the original MethodDeclarationSyntax
2. Applies only the necessary changes using:
   • .WithParameterList() - Update/remove parameters
   • .WithReturnType() - Fix return type (void/Task/ValueTask)
   • .WithModifiers() - Fix accessibility and static modifier
   • .WithTypeParameterList(null) - Remove generic type parameters
   • .WithBody() - Only filter out return statements when needed
3. Preserves everything else, including comments, whitespace, and formatting

This follows Roslyn best practices for syntax transformations and ensures minimal, targeted changes.

Changes

• Modified: src/Analyzers/MSTest.Analyzers.CodeFixes/Helpers/FixtureMethodFixer.cs

  • Rewrote FixSignatureAsync() to preserve method body and trivia
  • Updated helper methods to return proper Roslyn syntax types instead of generic SyntaxNode
  • Added defensive type check for MethodDeclarationSyntax

• Added Tests:

  • TestInitializeShouldBeValidAnalyzerTests.cs - Verify comments preserved for MSTest0008
  • TestCleanupShouldBeValidAnalyzerTests.cs - Verify comments preserved for MSTest0009
  • ClassInitializeShouldBeValidAnalyzerTests.cs - Verify comments preserved for MSTest0006

Impact

This fix improves all six MSTest fixture method analyzers that use FixtureMethodFixer:

• MSTest0001 (AssemblyInitialize)
• MSTest0002 (AssemblyCleanup)
• MSTest0006 (ClassInitialize)
• MSTest0007 (ClassCleanup)
• MSTest0008 (TestInitialize) ← Original reported issue
• MSTest0009 (TestCleanup)

Fixes #[issue_number]

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>MSTest0008 fixer seems to be suggesting to remove the comments</issue_title>
<issue_description>Let's take the following example. The code fixer suggests to remove the comments as well.

[TestInitialize]
public void TestSetup(TestContext tc)
{
    SomeCode();

    // Some comments;
}

</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #6697

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[Evangelink]

Remove using.