typings‑checker is a small command‑line tool that lets library authors write tests asserting that TypeScript either **does** or **doesn’t** produce type‑checking errors for specific code snippets, using `$ExpectError` and `$ExpectType` directives. It’s aimed at maintainers of type definition packages (e.g., DefinitelyTyped) who want to verify that their typings reject incorrect usage as well as accept correct usage.