Service Over a Fake Transport

Model in Solution: - record HttpReply(int status, String body) - interface HttpTransport { HttpReply send(String url); } - static class ApiClient with constructor (HttpTransport t) and String fetchUser(String id): - sends to "https://api.test/users/" + id - 200 → returns body - 404 → throws NoSuchElementException("user " + id) - 5xx → throws IllegalStateException("server error " + status) - static HttpTransport fakeTransport(Map<String, HttpReply> replies) — a transport returning the canned reply for the matching URL. The tests never open a socket; the fake IS the point.

Difficulty: intermediate