How do you test Node.js APIs with Jest and Supertest?

Question

Accepted Answer

**Jest** — test runner. **Supertest** — HTTP assertions.

```javascript
// app.js
const express = require("express");
const app = express();
app.use(express.json());
app.get("/users/:id", (req, res) => {
    res.json({ id: req.params.id, name: "John" });
});
app.post("/users", (req, res) => {
    res.status(201).json({ id: "1", ...req.body });
});
module.exports = app;

// app.test.js
const request = require("supertest");
const app = require("./app");

describe("Users API", () => {
    it("GET /users/:id returns user", async () => {
        const res = await request(app)
            .get("/users/123")
            .expect(200);

expect(res.body).toEqual({
            id: "123",
            name: "John",
        });
    });

it("POST /users creates user", async () => {
        const res = await request(app)
            .post("/users")
            .send({ name: "Jane" })
            .expect(201);

expect(res.body.name).toBe("Jane");
    });
});
```

**Key points:**
- Export Express app separately from server.listen.
- Use beforeAll/afterAll for DB setup/teardown.
- Mock external services.

Node.js: How do you test Node.js APIs with Jest and Supertest?