Startup takes a long time for unit tests referencing Microsoft.Testing.Platform.dll

Symptoms

Unit tests start running with a significant delay (e.g. 1 minute) in a test project that uses Microsoft.Testing.Platform.

Cause

Test exploration using the Testing Platform in a project never finishes correctly, occupying a resource shared among most discovery methods until timeout is hit.

Resolution

Disable Testing Platform support:

• Rider: Settings | Build, Execution, Deployment | Unit Testing | VSTest | Enable Testing Platform support
• ReSharper: ReSharper | Options | Tools | Unit Testing | Test Frameworks | VSTest | Enable Testing Platform support