Use assertContainsOnlyInstancesOf

Change-Id: I29bf6ac369af0c33bff0189a1ea935d71c34143e
Added test stub

Change-Id: I37e8d6df5f9febd49b118f82ac90759183dc1721
Include composer autoload file when present

Change-Id: Id10976373dfcc84f3836099b1c5e6c1b0a3b6142