Diagnosing Rider Unit Test Discovery Failures in .NET Solutions

Recognizable condition

After building a .NET solution in Rider, the Unit Test window shows no tests, lists them as Skipped, or fails to refresh even when dotnet test succeeds from the terminal.

Cause / diagnostic table

Possible cause	Typical symptom
Test project missing Microsoft.NET.Test.Sdk reference	Tests are not discovered; the window stays empty.
Target framework mismatch between test project and solution SDK	Tests appear as Skipped or the test runner reports an unsupported framework.
Rider’s built-in test runner disabled or outdated	Unit Test window shows a warning icon; no tests are listed after a build.
Corrupted .idea caches	Tests were visible before but disappear after a Rider restart or IDE update.

Ordered checks

1. Verify the test SDK reference
   • Open the test project’s .csproj file in Rider.
   • Look for a PackageReference element that includes Microsoft.NET.Test.Sdk.
   • If the element is missing or the version is older than the current stable release (e.g., <Version>17.0.0</Version>), note this as a finding.
2. Confirm target framework alignment
   • In the same .csproj, locate the <TargetFramework> tag.
   • Compare its value (e.g., net6.0) with the SDK version Rider is using (found via Help > About).
   • If they differ, record the mismatch.
3. Check Rider’s test runner settings
   • Navigate to Settings/Preferences > Tools > Unit Testing.
   • Ensure the checkbox Enable Rider unit test runner is ticked.
   • If disabled, enable it and note the setting.
4. Inspect IDE caches
   • Select File > Invalidate Caches and Restart….
   • After Rider restarts, observe whether the Unit Test window repopulates.
   • If tests reappear, the cache was likely corrupted.

Fixes tied to findings

• Missing test SDK: Add the following line inside the <ItemGroup> of the test project’s .csproj (adjust version as needed):

  <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />

  Save the file, let Rider restore packages, then rebuild.
• Target framework mismatch: Change the <TargetFramework> value to match the solution’s SDK (e.g., <TargetFramework>net6.0</TargetFramework>). Ensure all referenced projects support that framework; otherwise update them as well. Rebuild after saving.
• Test runner disabled: Toggle the Enable Rider unit test runner option, click Apply, and restart Rider if prompted.
• Corrupted caches: After invalidating caches (see step 4 above), Rider will rebuild its indices. No further action is required unless the problem persists.

Verification

1. Rebuild the solution (Build > Rebuild Solution).
2. Open the Unit Test window (View > Tool Windows > Unit Test).
3. Confirm that tests appear with icons indicating Not Run or Passed, not Skipped.
4. Run a single test via the gutter icon to ensure execution works and output appears in the Run window.
5. Perform a clean build (Build > Clean Solution) followed by a rebuild to ensure the issue does not reappear immediately.

Escalation criteria

If after completing all checks and applying the corresponding fixes the Unit Test window still shows no tests or continues to mark them as skipped:

• Collect Rider logs via Help > Diagnostic Tools > Show Log in Explorer and reproduce the issue with a minimal solution containing only the problematic test project.
• Attach the logs, the .csproj files, and a description of the environment (Rider version, OS, .NET SDK version) to a support ticket at JetBrains.
• Only escalate after the local diagnostics have been exhausted, as the support team will need the logs to identify deeper configuration or plugin conflicts.