Without any source code it is difficult to pinpoint the cause with certainty. You say:
Your setup of your SLC test development environment looks ok. How ever You don't say anything about your test environment. But if you test with, for example, a jar in the lib directory that contains the ExoplayerView class, the ExoplayerView class will not be included in your test.jar. In that case, the solution is to either include the ExoplayerView class-containing jar in your test environment, or to include the source code and all necessary classes of the ExoplayerView class-containing jar in your source (but in the second case you can difficult to talk about a wrapper).