Summary

This PR fixes an issue where custom TestMethodAttribute derived classes were incorrectly falling back to synchronous execution instead of using their async implementations.

Problem

The TestMethodAttribute constructor sets UseAsync = GetType() == typeof(TestMethodAttribute), which evaluates to false for derived classes. However, derived classes like UITestMethodAttribute, DataTestMethodAttribute, and STATestMethodAttribute were overriding the UseAsync property to return true directly:

private protected override bool UseAsync => true;  // Problematic

This caused inconsistent behavior where the framework would fall back to the synchronous Execute method instead of using the asynchronous ExecuteAsync method that these attributes implement.

Solution

Updated all derived TestMethodAttribute classes to use the same type-checking pattern as the base class:

// Before
private protected override bool UseAsync => true;

// After  
private protected override bool UseAsync => GetType() == typeof(UITestMethodAttribute);

This ensures that:

• Only the exact type uses the async execution path
• Classes that derive from these attributes must explicitly opt in to async behavior
• Behavior is consistent with the base TestMethodAttribute constructor logic

Files Changed

• UWP_UITestMethodAttribute.cs: UseAsync now checks for exact UITestMethodAttribute type
• WinUI_UITestMethodAttribute.cs: UseAsync now checks for exact UITestMethodAttribute type
• DataTestMethodAttribute.cs: UseAsync now checks for exact DataTestMethodAttribute type
• STATestMethodAttribute.cs: UseAsync now checks for exact STATestMethodAttribute type

Each change is minimal and surgical - exactly one line modified per file.

Impact

This fix ensures that custom test method attributes properly use their async execution paths, which is especially important for UI testing scenarios where execution must happen on specific threads.

Fixes #5707.

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.