It started as Testing on the Toilet, which was an effort to get people to actually care about unit-testing their code and software quality and writing maintainable code that doesn't break in 6 months. Later was expanded to Learning on the Loo, general tips and tricks, and then Testing on the Toilet became Tech on the Toilet. It's been going on for a good 20 years now, so that's about 1000 articles (they change them out weekly) and there aren't really 1000 articles you can write about unit testing.

The insight is actually pretty similar to Google's core business model: when you're going to the bathroom, there isn't a whole lot else you're doing, so it's the perfect time to put up a 2-3 minute read to reinforce a message that you want people to hear but might not get attention for otherwise.