When I updated Visual Studio to the latest version, 1 of my test projects stopped running tests and outputted this message:
Test project {} does not reference any .NET NuGet adapter. Test discovery or execution might not work for this project. It is recommended to reference NuGet test adapters in each test project in the solution.
UPDATED: I was using MS Test as opposed to any other test frameworks like Nunit or Xunit.
Ok, you can add Nuget packages as asked. But you can also try to disable the following setting (Tools->Options->Test): "For improved performance, only use test adapters in test assembly folder or as specified in runsettings file".
Let me know if it works for you.