Update copilot instructions with MTP v2/xunit v3 test commands

[Copilot]

The repository uses Microsoft.Testing.Platform v2 with xunit v3, but the copilot instructions still documented the legacy VSTest --filter syntax which doesn't work with this configuration.

Changes

Testing section expanded with working examples:

• Running individual test methods: -- --filter-method ClassName.MethodName
• Running test classes: -- --filter-class ClassName
• Wildcard filtering: -- --filter-method "*Pattern*"
• Trait-based filtering: -- --filter-trait "TraitName=value" and -- --filter-not-trait
• Framework targeting: --framework net9.0
• Listing tests: dotnet run -- --list-tests

Key syntax differences from VSTest:

• Options pass to test runner via -- separator, not directly to dotnet test
• Traditional --filter "TestCategory!=FailsInCloudTest" replaced with -- --filter-not-trait "FailsInCloudTest=true"
• Filter options are --filter-method, --filter-class, --filter-namespace, --filter-trait, not query expressions

Updated throughout:

• Testing section general guidance
• Common Tasks quick reference
• Troubleshooting tips

All commands were verified working before documentation.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• f.feedz.io
  • Triggering command: /opt/hostedtoolcache/dotnet/dotnet dotnet test --help (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Update the copilot instructions file of the repo with sample commands for executing tests in the repo. Be sure to account for the fact that we use MTP v2 and xunit v3, so the commonly used switches with dotnet test do not work. Include sample commands for running an individual test, an individual test class, or all tests for a given test project.
Test each of these commands before putting them into the copilot instructions file to make sure they work.

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[Copilot]

Pull request overview

This pull request updates the Copilot instructions to document the correct test command syntax for Microsoft.Testing.Platform v2 with xunit v3, replacing the outdated VSTest --filter syntax that no longer works with this configuration.

Changes:

• Added comprehensive testing section with 10+ working examples for MTP v2/xunit v3 test commands
• Updated all references from VSTest --filter syntax to MTP v2 syntax (--filter-method, --filter-class, --filter-trait, etc.)
• Documented key differences between VSTest and MTP v2 test filtering approaches

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.59%. Comparing base (c2d2c61) to head (2e537fd).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #855      +/-   ##
==========================================
+ Coverage   82.50%   82.59%   +0.09%     
==========================================
  Files         269      269              
  Lines       21321    21321              
  Branches     3071     3071              
==========================================
+ Hits        17590    17610      +20     
+ Misses       2709     2688      -21     
- Partials     1022     1023       +1     

Flag	Coverage Δ
Linux	82.20% <ø> (-0.03%)	⬇️
Windows	82.40% <ø> (+0.03%)	⬆️
macOS	82.12% <ø> (-0.02%)	⬇️

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