Are you trying to tests out some methods, but when it comes down to it your tests arent even running?
Typically they might have a blue exclamation point next to them and when you run all tests the output is something like:
0 tests run 0 tests passed 0 tests failed
This typically happens when you dont install the NUnit3TestAdapater.
Run this in the package manager console (tools > Nugest Package Manager > Package Manager Console)
Install-Package Nunit3TestAdapter
and then clean build your solution
and then run all tests and voila!
They should be running again (whether they pass or fail is up to you!)