Oh, I didn’t write tests for that. It’s too hard to test. Heard that before? I’ve made this argument myself in the past, but it’s only recently that I’ve figured out precisely why it’s a stupid argument. On the surface, and in context, it can seem reasonable. The code in question is often either interacting with the OS via system calls, or is involved in multi-process coordination, os else involves fiddly thread interaction. Read more

When writing a test, sometimes the only way to initially write the test is by duplicating the implementation code in the test to assert that the expected value is returned. This can happen for a number of reasons, but often arises because you are trying to test what is being performed, rather than how it’s being done, especially where the details of what’s being done are complicated and out of your control. Read more