Wow the test suite for otwarchive (the software that powers AO3) is fucking massive. Like, it just keeps going, and going, and going, and going, and going, and even more tests, and how about more tests, and another helping of tests, ...
And these are just the rspec tests, there's a whole second suite of cucumber tests that, if I'm understanding correctly, drives a whole-ass Chrome instance around to acceptance test the UI.
This isn't a critique to be clear, I'm just quite impressed.