thamerh / jest-express-api-testing-example

This project demonstrates how to test an Express API using Jest, covering unit tests for controllers, services, routers, and server configuration. It provides a simple, structured example for writing and running tests, generating coverage reports, and integrating Git hooks with Husky. Ideal for developers learning API testing in Node.js

Jest Express API Testing Example

This repository provides a simple example of how to test a Node.js API using Jest. The project is structured to demonstrate unit testing for an Express application, covering controllers, services, routers, and server configuration.

Table of Contents

• Project Structure
• Prerequisites
• Installation
• Running the API
• Testing the Code
• Generating Coverage Reports
• Git Hook Scripts

Project Structure

.
├── README.md
├── package.json
├── package-lock.json
├── src
│   ├── controller.js
│   ├── index.js
│   ├── router.js
│   └── service.js
└── test
    ├── controller.test.js
    ├── index.test.js
    ├── router.test.js
    └── service.test.js

Prerequisites

• Node.js (v18.17.1 or higher)
• npm (included with Node.js)

To manage Node.js versions, you can use nvm.

Installation

1. Clone the repository:

   git clone https://github.com/thamerh/jest-express-api-testing-example.git
   cd jest-express-api-testing-example

2. Install dependencies:

   npm install

Running the API

To start the Express server, run:

npm start

You can test the API endpoint using curl or any HTTP client:

curl http://localhost:3000/posts

Testing the Code

This project uses Jest for testing. To run the tests, use the following command:

npm test

Example output:

PASS  test/router.test.js
  should test router
    √ should test get posts (21 ms)

PASS  test/controller.test.js
  should test controller
    √ when #getPost method method succeeds (16 ms)
    √ when #getPost method method fails (1 ms)

PASS  test/service.test.js
  should test Service
    √ when #list method succeeds (17 ms)
    √ when #list method fails (1 ms)

PASS  test/index.test.js (5.998 s)
  should test server configuration
    √ should run the express server (39 ms)

Test Suites: 4 passed, 4 total
Tests:       6 passed, 6 total
Snapshots:   0 total
Time:        7.033 s

Generating Coverage Reports

Jest includes built-in coverage reporting using Istanbul. To generate a coverage report, run:

npm run coverage

This will produce a coverage report in the terminal and generate an HTML report in the coverage/lcov-report directory.

Example terminal output:

PASS  test/index.test.js
PASS  test/router.test.js
PASS  test/controller.test.js
PASS  test/service.test.js

---------------|---------|----------|---------|---------|-------------------
File           | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
---------------|---------|----------|---------|---------|-------------------
All files      |   95.83 |      100 |   85.71 |   95.83 |                   
 controller.js |     100 |      100 |     100 |     100 |                   
 index.js      |   83.33 |      100 |       0 |   83.33 | 9                 
 router.js     |     100 |      100 |     100 |     100 |                   
 service.js    |     100 |      100 |     100 |     100 |                   
---------------|---------|----------|---------|---------|-------------------

Test Suites: 4 passed, 4 total
Tests:       7 passed, 7 total
Snapshots:   0 total
Time:        1.459 s

Git Hook Scripts

This project uses Husky to manage Git hooks. A pre-commit hook is configured to run tests before each commit. If the tests fail, the commit will be aborted.

Example output when committing:

$ git commit -am 'feat: add basic husky support'
> jest test/**.test.js

PASS  test/index.test.js
PASS  test/service.test.js
PASS  test/router.test.js
PASS  test/controller.test.js

Test Suites: 4 passed, 4 total
Tests:       7 passed, 7 total
Snapshots:   0 total
Time:        1.812 s
Ran all test suites matching /test\/controller.test.js|test\/index.test.js|test\/router.test.js|test\/service.test.js/i.
[master 508a8eb] feat: add basic husky support
4 files changed, 16 insertions(+), 3 deletions(-)
create mode 100644 .husky/.gitignore
create mode 100755 .husky/pre-commit

---

Feel free to explore the code and adapt it to your needs. If you have any questions or suggestions, please open an issue or submit a pull request. Happy coding! 🚀

Made By

• @thamerh