Writing tests that test failure

Often forgotten because most of the time you want to proove that your code runs. Yes I know we all tend to be lazy. But to be complete in a sense of Sir Carl Popper you also have to falsify your assumption. You are forced to think about deeper about what your code does and what it should not do. But even further you proove that exceptions are treated correct in case of an error or worse like it happened to me it gets swallowed. I was about to refactor an ancient piece of software written in the early days of Java development. I wrote a test for a new feature and was happy to see my test was successfull. But writing a failure test I recognized that every exception was swallowed by an nice try {} catch (Exception) block just because this test failed.