Bug: Unable to cancel/abort Test Run (Stop button is unresponsive)

[Dor-bl]

Describe the Issue

When running tests via the Test Explorer using C# Dev Kit, clicking the "Stop Execution" (cancel) button does not terminate the active test run. The UI shows the spinner indefinitely, and the underlying process appears to ignore the cancellation request.

In the attached reproduction, I am running Appium.Net.Integration.Tests. When I attempt to stop the run mid-execution (during the build/discovery or early execution phase), the stop button interacts visually (click registered) but fails to actually stop the operation.

Steps To Reproduce

Open a C# solution with a test project (specifically one that might take time to build or initialize, like Integration tests).

Go to the Testing sidebar.

Click the Run Tests (play) button on a test suite (e.g., Appium.Net.Integration.Tests).

While the tests are running (spinner is active), click the Stop (square icon) button next to the running test node or in the Test Results toolbar.

Screen.Recording.2025-12-25.at.0.00.53.mov

Expected Behavior

The test run should abort immediately (or within a reasonable timeout), returning the state to "Not Running" and stopping the background build/test process.

Environment Information

OS: macOS

VS Code Version: 1.106.3 (Universal)

Extension Version: C# Dev Kit v1.14.4 (Pre-Release)

Test Framework: NUnit