Error when running unit tests in visual studio: Test-case objects missing

I know this won't answer the OP's question, since he/she has tried it, but maybe it will help someone else.

For me a simple restart of Visual Studio solved the Test-case objects missing for the following elements: ... Rebuild the project and try again problem.

I experienced this error after removing all nuget packages as I had changed my .net version and did not need any of them to compile.

After re-installing the MSTest.TestAdapter nuget package ReSharper started running my unit tests again as expected.

Install-Package MSTest.TestAdapter