[heavenlyblue]

You label a few photos yourself and then check if the labels still correspond in the newer versions of the program.

Then when you edit any parts of the code and the test suite breaks - you can see that some of the invariants had been broken.

This is even more important for python, as at least having a simple test suite can already tell whether your environment is sane. And that's about 90% of the newcomer's time saved.

[adrianN]

That is completely different from formal verification. Simple testing is something all researchers that I know do, quite extensively actually.