Fix documentation to use --treenode-filter instead of unsupported --filter syntax

[Copilot]

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• If this is a new feature or piece of functionality, have you started a discussion and gotten agreement on it?
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Description

TUnit doesn't support VSTest's --filter CLI option. Documentation incorrectly showed using --filter "Category=X" which results in "Unknown option '--filter'" errors.

Changes

• CI/CD Pipeline Documentation (docs/docs/examples/tunit-ci-pipeline.md)

  • Updated GitHub Actions and GitLab CI examples to use correct tree-node filter syntax
  • Added .NET 10 SDK syntax note

• Performance Best Practices (docs/docs/advanced/performance-best-practices.md)

  • Updated CI/CD optimization examples to use correct filter syntax

Syntax

Incorrect (VSTest):

dotnet test --filter "Category=Unit"

Correct (TUnit):

# .NET 9 and older
dotnet test -- --treenode-filter "/*/*/*/*[Category=Unit]"

# .NET 10+
dotnet test --treenode-filter "/**[Category=Unit]"

Both dotnet run and dotnet test support the tree-node filter syntax with the -- separator (not needed in .NET 10+).

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Cannot filter by category</issue_title>
<issue_description>According to the website (https://tunit.dev/docs/examples/tunit-ci-pipeline/#filter-tests-by-category) I should be able to run:

# Unit tests (fast)
- name: Unit Tests
  run: dotnet test --filter "Category=Unit"

# Integration tests (slower)
- name: Integration Tests
  run: dotnet test --filter "Category=Integration"

However, running dotnet test --filter "Category=Integration" yields the following output:

Exit code: 5
  Standard output:
  ████████╗██╗   ██╗███╗   ██╗██╗████████╗
  ╚══██╔══╝██║   ██║████╗  ██║██║╚══██╔══╝
     ██║   ██║   ██║██╔██╗ ██║██║   ██║
     ██║   ██║   ██║██║╚██╗██║██║   ██║
     ██║   ╚██████╔╝██║ ╚████║██║   ██║
     ╚═╝    ╚═════╝ ╚═╝  ╚═══╝╚═╝   ╚═╝

     TUnit v1.5.1.0 | 64-bit | Darwin 25.1.0 Darwin Kernel Version 25.1.0: Mon Oct 20 19:34:05 PDT 2025; root:xnu-12377.41.6~2/RELEASE_ARM64_T6041 | osx-arm64 | .NET 8.0.22 | Microsoft Testing Platform v2.0.2

     Engine Mode: SourceGenerated

  Unknown option '--filter'

and doesn't run any tests.</issue_description>

<agent_instructions>TUnit doesn't support the --filter cli command.
Update the docs to remove the incorrect information, and use the --treenode-filter. Make sure to use the correct syntax for the treenode filter.</agent_instructions>

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

@thomhurst I'll fix that. If you're using the .net 10 Sdk try:

dotnet test --treenode-filter "/**[Category=Unit]"</comment_new>

• Fixes Cannot filter by category #4019

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Pull request overview

This PR fixes critical documentation errors where TUnit-specific CLI syntax was incorrectly shown using VSTest's --filter option, which TUnit does not support. The changes replace incorrect filter syntax with TUnit's --treenode-filter option across CI/CD examples.

• Updated all examples from --filter "Category=X" to correct -- --treenode-filter "/*/*/*/*[Category=X]" syntax
• Added helpful notes about .NET 10 SDK's simplified syntax (--treenode-filter "/**[Category=X]") that doesn't require the -- separator
• Ensures users can successfully filter tests by category in CI/CD pipelines

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/docs/examples/tunit-ci-pipeline.md	Fixed GitLab CI and GitHub Actions examples to use correct --treenode-filter syntax; added .NET 10 SDK note
docs/docs/advanced/performance-best-practices.md	Fixed CI/CD optimization examples to use correct --treenode-filter syntax; added .NET 10 SDK note