Test Your Babel Configuration
Having maintained a client-heavy web application for the last few years, there's one dependency that has routinely broken builds during my weekly dependency upgrades: Babel.
That's not really a surprise. Babel is complicated, you can go through its source code to see that. There are so many permutations of different configurations that it's pretty much impossible to test everything.
What makes this worse is that Babel is a development tool. My tests rely on it to work to even run! So, what can I do? Well, the part that determines Babel's behaviour is my configuration, so I can at least test that.