This project provides compile-time type testing utilities, similar to Jest's `expect` but for TypeScript types. It allows developers to write assertions about type structures that are checked at compile time, helping prevent type regressions when code changes. The library exports `expectTypeOf` which can be used to verify function signatures, object shapes, generics, and more, with intuitive methods like `.toEqualTypeOf()`, `.toBeString()`, `.parameters`, and `.returns`. It's particularly useful for library authors who want to ensure their public APIs maintain correct type contracts over time.