Mark TestMetadataGenerator output with GeneratedCode attribute

[Copilot]

The TestMetadataGenerator was not marking generated code with [GeneratedCode] or [ExcludeFromCodeCoverage] attributes, preventing code coverage tools from properly excluding it.

Changes

• Added [GeneratedCode] and [ExcludeFromCodeCoverage] attributes to generated test metadata classes
• Updated 86 snapshot tests to reflect the new output

Generated Code

Before:

namespace TUnit.Generated;
internal sealed class TUnit_MyTests_Test_TestSource : ITestSource
{

After:

namespace TUnit.Generated;
[global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverageAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("TUnit", "1.0.0.0")]
internal sealed class TUnit_MyTests_Test_TestSource : ITestSource
{

This aligns with existing patterns in InfrastructureGenerator and DynamicTestsGenerator.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Bug]: Mark TestMetadataGenerator code with generated code attribute</issue_title>
<issue_description>### Description

The code generated by TUnit.Core.SourceGenerator.Generators.TestMetadataGenerator is not marked with the [GeneratedCode] attribute, which makes it harder to exclude from code coverage reports.

Expected Behavior

All code generated by source generators would be marked with [GeneratedCode]. If appropriate, it could also be marked with [ExcludeFromCodeCoverage] as well.

Actual Behavior

The code, which is generated in the TUnit.Generated namespace, is not marked with any attributes to signify it is auto-generated.

Steps to Reproduce

Use <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles> in a project file to see the generated code and note it is not marked with attributes.

TUnit Version

1.13.0

.NET Version

.NET 10

Operating System

Windows

IDE / Test Runner

Other (please specify in additional context)

Error Output / Stack Trace

Additional Context

This happens during build, not during test execution, although the impact mostly affects code coverage reports.

IDE-Specific Issue?

• I've confirmed this issue occurs when running via dotnet test or dotnet run, not just in my IDE</issue_description>

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

• Fixes [Bug]: Mark TestMetadataGenerator code with generated code attribute #4688

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[claude]

Code review

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

This PR correctly adds [GeneratedCode] and [ExcludeFromCodeCoverage] attributes to the TestMetadataGenerator output, following the existing pattern used in InfrastructureGenerator and DynamicTestsGenerator. All 86 snapshot tests have been properly updated with .verified.txt files (no .received.txt files committed), which aligns with the snapshot testing requirements in CLAUDE.md.

[claude]

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Code review

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

Summary

This PR cleanly adds [GeneratedCode] and [ExcludeFromCodeCoverage] attributes to generated test metadata classes, addressing issue #4688. The change:

✅ Follows existing patterns - Uses the exact same attribute pattern as InfrastructureGenerator.cs and DynamicTestsGenerator.cs
✅ Proper snapshot testing - All 86 .verified.txt files correctly updated, no .received.txt files committed
✅ CLAUDE.md compliant - Meets all critical rules (dual-mode N/A, snapshot testing ✓, performance ✓, AOT compatible ✓)
✅ No bugs - Syntax correct, attributes properly qualified, correct placement

The implementation is straightforward and will improve code coverage reporting by properly marking auto-generated code for exclusion from coverage metrics.

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