Why is the Visual Studio 2015/2017/2019 Test Runner not discovering my xUnit v2 tests

Answer 1

I had the same issue with Visual Studio 2019. Just Installed the following NuGet packages and the issue was solved.

1). xUnit

2). xunit.runner.visualstudio

3). Microsoft.TestPlatform.TestHost

4). Microsoft.NET.Test.Sdk

Answer 2

Disclaimer: it is not about xunit with visual studio 2015, but Visual Studio 2017 with a UWP unit test application (MSTest). I got to this thread searching the same thing so maybe someone else will do the same :)

The solution for me was to update the nuget packages for MSTest.TestAdapter and MSTest.TestFramework. It seems that when you create a unit test app for UWP you don't automatically get the latest versions.

Answer 3

Here is the solution that worked for us. Not the best but maybe one can benefit.

Background:

• Our scripts were developed with VS 2013 and used NUnit VS Adapter 2.1..
• Recently we migrated to VS 2017 and when open the same solution - test wouldn't show in the Test Explorer

Upon Build we would see this message:

[Informational] NUnit Adapter 3.10.0.21: Test discovery starting
[Informational] Assembly contains no NUnit 3.0 tests: C:\ihealautomatedTests\SeleniumTest\bin\x86\Debug\SeleniumTest.dll
[Informational] NUnit Adapter 3.10.0.21: Test discovery complete

Solution (temporary):

• Uninstall NUnit Adapter 3.10...
• Install NUnit VS Adapter 2.1..

Now the Tests are shown.

Answer 4

I've been struggling with this all afternoon whilst working with an ASP Core project and xUnit 2.2.0. The solution for me was adding a reference to Microsoft.DotNet.InternalAbstractions

I found this out when trying to run the test project manually with dotnet test which failed but reported that InternalAbstractions was missing. I did not see this error in the test output window when the auto discovery failed. The only info I saw in the discovery window was a return code, which didn't mean anything to me at the time, but in hindsight was probably indicating an error.

Answer 5

Do make sure that you haven't written your unit tests in a .NET Standard 2.0 Class Library. The visualstudio runner does not support running tests in netstandard2.0 class libraries at the time of this writing.

Check here for the Test Runner Compatibility matrix:

https://xunit.github.io/#runners

Answer 6

There is one other reason that can cause Test Explorer not showing any tests, and it has to do with the new portable .pdb file format introduced with Visual Studio 2017 / for .NET Core which can break some VS tooling. (Background: See the bug report "Mono.Cecil causes OutOfMemoryException with new .csproj PDBs".)

Are your tests not found because of the new portable .pdb (debug symbols) format?

• Open the Output window.
• Change drop-down selection for Show output from to Tests.

• If you see output like to the following (possibly repeated once for each of your tests), then you've got the problem described in this answer:

  Exception System.OutOfMemoryException, Exception converting <SignatureOfYourTestMethod>
  Array dimensions exceeded supported range.
  

If yes, do this to resolve the problem:

• Open your test project's Properties (select the test project in Solution Explorer and press Alt+Enter).
• Switch to the Build tab.
• Click on the Advanced... button (located at the very end of that tab page).
• In the drop-down labelled Debugging information, choose none, pdb-only, or full, but NOT portable. It is this last setting that causes the tests to not be found.
• Click OK and clean & rebuild your project. If you want to be extra sure, go to your test project's output directory and clean all .pdb files before rebuilding. Now your tests should be back.