This article's about a year and a half old. We have pretty good unit test coverage on a good chunk of our code (especially core stuff), though admittedly not e

This article's about a year and a half old. We have pretty good unit test coverage on a good chunk of our code (especially core stuff), though admittedly not everything. Some groups put particular emphasis on this (e.g. the messages team is great about testing), and it shows in the reliability of their products. Even better, they end up building frameworks that make it easier for the rest of engineering to write tests, and drive the whole ecosystem forward.