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