This is a big reason why I prefer property testing to unit testing. One can think of focusing on the abstract behavior and invariants of the code, rather than just the expected outputs for specific inputs, as being somewhat akin to taking the time to plan out your experiment and the statistical tests you want to perform ahead of time, do your power analysis, etc. It's a fair bit more up-front work, but helps to ensure that you have a crystal clear idea of what you're going to do before you start doing it.