Test the GalleryPhpVm. These are passthrough functions so all we do is perform a smoke test to make sure that the basic arguments are getting passed through correctly.
Unregister a specific factory implementation or all implementations of a spefific type temporarily for this test.
You need to call _markFactoryForCleanup() before changing the factory during a test. To unregister all implementations of a specific type, leave implId and className empty.