Bug Making [UnityTest] work with [TestCaseSource]

I'm trying to create a parametric Unity play mode test (e.g: one that spans multiple frames).
Here's an example of what i'm trying to do:

Code (CSharp):

1. [UnityTest]
2. [TestCaseSource("LevelPaths")]
3. public IEnumerator LoadLevel_VerifyWeAreGood(string levelPath)
4. {
5.     yield return null;
6.  
7.     // Test Logic Here
8. }

When running this in the test runner, the test fails, and i am getting this error:

What am i doing wrong here?

 

Awesome thanks @superpig
now just look at my other thread and we can call it a day