forwardemail/supertest ? reverse-engineered prompt

Build me a small Node.js testing helper for HTTP servers, something that makes it easy to write clean, fluent tests against an app or a live URL.

I want to be able to pass in an Express app or a server function, then call things like get, post, send, set headers, auth, and chain expectations for status, response headers, and body. It should work with common test styles, so callbacks, promises, and async await all feel natural. If the server is not already listening, just handle that for me. I also want cookie handling through an agent, support for multipart uploads and form data, and a way to test over http2 when needed.

Keep it simple and focused on HTTP assertions, but make sure the API feels friendly and readable. If you need to check current docs for request handling details, look them up online.