Testing React Components

Part of the React course

You change one line in a shared component and then spend twenty minutes clicking around the app checking that nothing else broke. Next week you change it again, and do the same twenty minutes. Eventually you stop changing it at all, because the checking is not worth it, and the code slowly rots around a piece nobody dares touch.

A test is that clicking-around written down once and run by a machine in a second. Its real value is not catching bugs today, when you already know the code works. It is that six months from now you can rename something, delete a branch, or rewrite a component from scratch, run one command, and get an honest answer about whether you broke anything.