Supertest for HTTP assertions in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Supertest used for in Express applications?

Supertest is a library used to test HTTP endpoints in Express apps by simulating requests and checking responses without needing the app to listen on a real network port.

beginner

How do you start a Supertest test for an Express app?

You import Supertest and pass your Express app to it, like: <code>const request = require('supertest')(app);</code> Then you can chain HTTP methods like <code>.get()</code> or <code>.post()</code> to test routes.

beginner

What method do you use in Supertest to check the HTTP status code of a response?

You use the .expect(statusCode) method to assert the response status code matches what you expect, for example .expect(200).

intermediate

How can you test JSON response content with Supertest?

You can use .expect('Content-Type', /json/) to check the response type and .expect(responseBody) to check the exact JSON returned, or use a function inside .expect() to run custom checks on res.body.

intermediate

Why is Supertest preferred over manual HTTP requests in testing Express apps?

Supertest runs tests directly on the Express app instance without needing to open network ports, making tests faster, more reliable, and easier to write and maintain.

Which of these is the correct way to start a Supertest request for an Express app named 'app'?

A const request = supertest(app.listen());

B const request = supertest.create(app);

C const request = new supertest(app);

D const request = require('supertest')(app);

You import Supertest and immediately call it with your Express app instance: require('supertest')(app).

How do you check that a GET request to '/users' returns status 200 using Supertest?

A request.get('/users').checkStatus(200);

B request.get('/users').status(200);

C request.get('/users').expect(200);

D request.get('/users').assert(200);

The correct method to assert status code is .expect(200).

Which method lets you test the response body content in Supertest?

A .expect()

B .assertBody()

C .checkBody()

D .expectBody()

The .expect() method can be used to check response body content by passing expected data or a function.

What does Supertest NOT require to run tests on an Express app?

A The app to listen on a network port

B The Express app instance

C Node.js environment

D A test runner like Jest or Mocha

Supertest works directly with the app instance and does not need the app to listen on a real network port.

Which of these is a benefit of using Supertest for HTTP assertions?

A It requires manual HTTP requests to external servers

B It allows fast, reliable testing without network overhead

C It slows down tests by opening network ports

D It only works with REST APIs, not Express apps

Supertest allows fast and reliable testing by running requests directly on the Express app instance without network overhead.

Explain how you would write a Supertest test to check that a POST request to '/login' returns a 401 status when credentials are wrong.

Think about chaining methods to send data and check response.

Describe why Supertest is useful for testing Express apps compared to manual HTTP requests.

Focus on speed, reliability, and ease of use.