Jest or Vitest setup for Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of using Jest or Vitest with an Express app?

They help test your Express app's code automatically to catch errors early and ensure it works as expected.

beginner

Which file usually contains the Express app setup for testing?

A separate file like <code>app.js</code> or <code>server.js</code> exports the Express app so tests can import it without starting the server.

intermediate

How do you tell Jest or Vitest to run tests in a Node environment for Express?

Set the test environment to node in the config file or use @jest-environment node at the top of test files.

intermediate

What is the role of supertest in testing Express apps with Jest or Vitest?

supertest simulates HTTP requests to your Express app so you can test routes and responses without running a real server.

beginner

How do you run tests with Vitest after setup?

Use the command npx vitest or add a script like "test": "vitest" in package.json and run npm test.

Which package helps simulate HTTP requests to test Express routes?

A dotenv

B express-session

C cors

D supertest

supertest is used to simulate HTTP requests in tests for Express apps.

What environment should Jest or Vitest use to test Express apps?

A node

B jsdom

C browser

D react

Express apps run on Node.js, so the test environment must be set to node.

Where should you export your Express app for testing?

A Inside the test file

B In a separate app file like <code>app.js</code>

C In <code>package.json</code>

D In <code>node_modules</code>

Exporting the app from a separate file allows tests to import it without starting the server.

Which command runs Vitest tests if configured in package.json scripts?

A npm test

B npm run start

C node vitest

D vitest start

npm test runs the test script, which can be set to vitest.

Why avoid starting the Express server in test files?

A It slows down tests

B It causes port conflicts

C All of the above

D It makes tests less isolated

Starting the server can slow tests, cause conflicts, and reduce test isolation.

Explain how to set up Jest or Vitest to test an Express app's routes.

Think about how to import the app, simulate requests, and configure the test runner.

Describe why using supertest is helpful when testing Express apps with Jest or Vitest.

Imagine testing your app's web pages without opening a browser.