While that's true, you don't want to end up in a situation where the test is enforcing coupling which makes it harder to refactor your code. So, for instance, if you have tests that assert whether the method tested calls another method with certain parameters in a certain order, then you're enforcing coupling between the two methods. If you refactor the code to have the first method return a result and then use that result to call the second method, then you also have to update the tests. But they shouldn't have to be updated since the overall logic hasn't changed. If, instead, you test the logic of each method individually, then you can refactor and not have to update the tests.