API tests with Supertest

📘What it really is

• Supertest sends real HTTP requests to your Express app without starting a server on a port (that's why app and server were separated in Module 42):

import request from "supertest";
import { app } from "../src/app.ts";

it("refuses to list enquiries when signed out", async () => {
  const res = await request(app).get("/enquiries");
  expect(res.status).toBe(401);
});

it("creates an enquiry with valid data", async () => {
  const agent = request.agent(app);                 // keeps cookies, like a browser
  await agent.post("/auth/sign-in").send({ email: "staff@test.in", password: "test-password-123" });
  const res = await agent.post("/enquiries").send(validEnquiry);
  expect(res.status).toBe(201);
  expect(res.body.status).toBe("new");
});

it("returns field errors for invalid data", async () => {
  const res = await signedInAgent.post("/enquiries").send({ name: "" });
  expect(res.status).toBe(422);
  expect(res.body.fields.email).toBeDefined();
});

• API tests check what clients actually experience: status codes, response bodies, cookies, headers, and that error responses contain no stack traces.

• Use a test configuration: a temporary data folder (or in-memory repository) and test users, so tests never touch real data.