Supertest
- Node.js course
- Advanced
- Lesson 74/83
- 5 min
Learn HTTP testing with supertest.
Supertest
Supertest is a library that lets you test Express applications without making real HTTP requests. It invokes the app in memory; it does not open a real port. This makes tests fast and isolated.
Example: const request = require("supertest"); const app = require("./app"); request(app).get("/users").expect(200);. This sends a GET /users request to app in memory and expects the response to be 200. Supertest skips Express's app.listen; instead it calls http.createServer(app) directly. So the app.listen code is not invoked for tests. Supertest's chain structure lets you write readable tests: request(app).get("/").expect(200).expect("Content-Type", /json/).
The chain test structure
Supertest's power is in its chain structure. request(app).get(path).expect(status) sends the request and verifies the response status in a single line. Multiple .expect calls can also be chained.
Example: request(app).post("/users").send({ name: "Ayşe" }).expect(201).expect("Content-Type", /json/);. This sends a POST /users request with the body { name: "Ayşe" }; it expects the response to be 201 and to have a JSON content type. .send sets the body, .expect does the assertion. The chain improves the readability of the test. If multiple assertions are chained, all must pass; if any fails, the test fails. So each test should focus on a single behavior.
Practice Write a GET test with supertest
Import the supertest module with require. Import app with require("./app"). After const request = require("supertest"), print "supertest ready" with console.log.
Starter code
// Import supertest and app
// write here
// Print "supertest ready"
// write hereSample solution
const request = require("supertest");
const app = require("./app");
console.log("supertest ready");Expected output
supertest ready
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Complete the request call
const request = require(____);const request = require("supertest");Explanation: The supertest module is loaded as "supertest".
2 Match each method to its role
| Term | Meaning |
|---|---|
request(app) |
Starts a request |
.get/.post |
Sets the HTTP method |
.send |
Adds a body |
.expect |
Does an assertion |
3 Why doesn't supertest open a real port?
request(app).get('/users')- Because tests are slow
- Because Express doesn't run
- Because it skips app.listen
- Because it invokes app in memory Correct answer
Explanation: Supertest invokes app in memory.