If you’re receiving the follow error messages while setting up xUnit or NUnit for a project:

Unable to find tests for C:\[my purdy path]\Tests.dll


No test is available in C:\[My purdy path]\NUnitDemo.csproj.
Make sure that test discoverer & executors are registered and
platform & framework version settings are appropriate and try again.

Besides installing the obvious nugets (NUnit for example below)…

NUnit nugets

… you also need to install the Microsoft.NET.Test.Sdk as well.

Microsoft test SDK

Clean and build solution and run your tests. Hopefully all tests will be found and ran now!