I've just installed Visual Studio 2019 Professional and I noticed some misbehavior if I compare it to the VS 2017 which I used to work with.
The Test Explorer window
In the VS 2017 when I open a project, that already had been opened previously, I see all the tests in the Test Explorer. In the VS 2019 the window is empty until I rebuild the solution.
If I rebuild the solution and all the xUnit tests are discovered I cannot click on any single test. I can click on all the folders in the hierarchy, but not on the leaf node with the actual test - so I don't see the exception if the test fails or any further details. If I right-click on the test, the possibility Open Test is always disabled.
In VS 2017 the same solution is working fine without any changes.