Testing the right thing 

One of the most important considerations when writing any test, whether a granular unit test or a far-reaching E2E test, is the question of what to test. It's entirely possible to test the wrong thing; doing so can give us false confidence in our code. We may write a huge test suite and walk away grinning, thinking that our code now fulfills all expectations and is utterly fault-tolerant. But our test suite may not test the things we think it does. Perhaps it only tests a few narrow use cases, leaving us exposed to many possibilities of breakage. Or perhaps it conducts tests in a way that is never emulated in reality, leading to a situation where our tests don't protect us from failures in production. To protect us ...

Get Clean Code in JavaScript now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.