Visual Studio 15.8.1 not running MS unit tests

Question

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 N

Answer 1

Adding NuGet packages doesn't work for me.

Disable the following setting (Tools->Options->Test): "For improved performance, only use test adapters in test assembly folder or as specified in runsettings file" works.