Unit tests not discovered in Visual Studio 2019

Question

The tests are present at Test Explorer but run command has no effect.

Looking at Output windows, for Test outputs it shows many errors like this:

 MSTestAdapter failed to discover tests in class 'UnitTests.Adhoc' of assembly 'some test.dll' because Method not found: 'System.String Microsoft.VisualStudio.TestTools.UnitTesting.TestMethodAttribute.get_DisplayName()'..

Answer 1

For me, the other solutions didn't work as I eg did not have a reference to the package 'Microsoft.VisualStudio.TestPlatform.TestFramework'. It turned out that the solution for me was updating the Target Framework of the test projects from .NET Core 2.0 to .NET Core 3.1. Everything was working as before when changing that. I'm not sure what caused the issue, but I think it was a combination of three packages. For full reference, these are the ones (with version) I am now using with .NET Core 3.1:

Microsoft.NET.Test.SDK

MSTest.TestAdapter 2.1.1

MSTest.TestFramework 2.1.1

On Visual Studio 16.5.2

Answer 2

Found out that had some assembly conflict not signal by visual studio as usual on the references tree node.

Removing Microsoft.VisualStudio.TestPlatform.TestFramework reference and adding again did the trick.

Here de difference at the project file:

Before:

<Reference Include="Microsoft.VisualStudio.TestPlatform.TestFramework, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
  <HintPath>..\..\packages\MSTest.TestFramework.2.0.0\lib\net45\Microsoft.VisualStudio.TestPlatform.TestFramework.dll</HintPath>
</Reference>
<Reference Include="Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
  <HintPath>..\..\packages\MSTest.TestFramework.2.0.0\lib\net45\Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions.dll</HintPath>
</Reference>

After:

<Reference Include="Microsoft.VisualStudio.QualityTools.UnitTestFramework, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL" />

Answer 3

My problem was that I had tests in one specific class that weren't recognized.

Turns out I'd cut and pasted a TestInitialize method that contained a TestContext that I wasn't using. For instance:

[TestInitialize]
public void ClassInitialize(TestContext context)

When I removed the unused TestContext all my tests were recognized:

[TestInitialize]
public void ClassInitialize()

Answer 4

You can go to the test options (Test -> Options) and turn up the logging level to trace, and then you might find more information. for me, it was because the test classes were not public, even though te.exe (https://docs.microsoft.com/en-us/windows-hardware/drivers/taef/ ) found the tests fine even when the classes were non public

[MSTest][Discovery][C:\Users\mgrandi\Code\git\blah\src\Services\blah\Test\blah.Tests\bin\Debug\net472\blah.Tests.dll] UTA001: TestClass attribute defined on non-public class blah.Tests.blah.Common.BondObjectSanitizerTest