Testing Types in TypeScript
As your TypeScript usage gets more advanced, it can be extremely helpful to have utilities around that test and verify your types. Like unit testing, but without needing to set up Jest, deal with mocking, etc. In this post, we’ll introduce this idea. Then we’ll dive deeply into one particular testing utility that’s surprisingly difficult to create: a type that checks whether two types are the same.
This post will cover some advanced corners of TypeScript you’re unlikely to need for regular application code. If you’re not a huge fan of TS, please understand that you probably won’t need the things in this post for your everyday work, which is fine. But if you’re writing or maintaining TypeScript libraries, or even library-like code in your team’s app, the things we discuss here might come in handy.
Then mouse over the X and verify that it’s true, which it is. But we don’t settle for ad hoc testing like that with normal code, so why would we with our advanced types?
