you're describing two different types of tests. one kind is the acceptance test, where you write a test that specifies correct behavior under normal circumstan

you're describing two different types of tests. one kind is the acceptance test, where you write a test that specifies correct behavior under normal circumstances (including expected error scenarios). the other kind is a regression test, where you reproduce a discovered bug in a test environment, then fix it, and make sure that the test covers the fixed code to confirm that the bug is no longer occurring. both types of tests are important and for different reasons. they aren't mutually exclusive and they aren't addressing the same problem.