Add CodeLense visibility for xUnit theory tests.

[DTeuchert]

Add CodeLense visibility for xUnit theory tests, which can be tested with XunitTests.TestCase3.cs.
Solves #61

[stefanforsberg]

Hey @DTeuchert and thanks for the PR! At the moment it's not possible to run a single test with theories. The command generated (for instance --filter FullyQualifiedName~XunitTests.TestClass3.Pass2(value: 2)) can not be executed. I'm not sure if xunit supports running a specific theory or not.

Would you mind looking into if you could make that work?

[DTeuchert]

To run theories your command must be modified to --filter FullyQualifiedName~XunitTests.TestClass3.Pass without specify the testdata in parameters. In the pull request I have made a replacement.

Another problem occured by running the filter parameter (FullyQualifiedName) by using "~" which behaves similar to a like (for instance runTestByName(XunitTests.TestClass3.Pass) also tests the testcase Pass2). Therefore I distinguish whether the test is executed on a folder (class or root) or for a special test case. For running a single test runTestByName needs to specify the filter parameter (FullyQualifiedName) by "=".

[stefanforsberg]

Currently only xunit supports FQN (until #51 is merged anyway) so by using = instead of ~ you can not run specific tests for nunit or mstest.

So that perhaps leads to unit test framework specific code which I'd rather avoid if possible. But the current model of running more tests than expected (Pass, Pass2... PassN) is not ideal either. Hmm.

[DTeuchert]

I agree that framework specific code should be avoided. I suggest that I will revert the changes regarding FQN. The replacement in the testName is necessary to run single theory test cases.