I changed asserts with more specific assert methods.
e.g.: from assertTrue(sth == None) to assertIsNone(*) or
assertTrue(isinstance(inst, type)) to assertIsInstace(inst, type)
or assertTrue(not sth) to assertFalse(sth).
The code gets more readable, and a better description will be shown on fail.
Change-Id: If6aad8681aab7c9a41d65a4f449d8abbe3e64616