The specialist tester will not take anything as obvious, every assumption should be tested and approved before he can put the “Approval” signature.
One of the most annoying testers I worked with where the once who told me that some tests are not important because they already have tested them two months ago or in some cases the developer told them that the bug he just fixed will not affect any components during the integration of the code parts.
For me such testers should be abandoned from the testing world because they failed to do their job. Our job is to make sure that all requirements applied with success and the only way we can do it with success is to trust our testing sense and questioning everything without assuming that something will work just because it looks fine or someone told us that we don’t need to waste our time to test it.
For me the real specialist will know how to process the information he gets and analyze it based on skillful “Risk Analysis”, and only after he analyze and understand the risk factor he then can take the right decisions and decide how to handle the assumption provided to him by any other collogue.