Testing A Rest Api By Using Javascript

Introduction

Testing is an essential part of software development. In the context of REST APIs, testing becomes even more critical as it helps to ensure that the API behaves as expected and that it can handle various scenarios.

In this article, we will explore how to use some of the most popular testing libraries in Node.js to create tests for a REST API. Specifically, we will cover Mocha, Chai, Chai-HTTP, Sinon, Mocha JUnit Reporter, Istanbul, and NYC.

Installing the Libraries

Before we dive into the details of each library, we need to install them. To do so, we will use the Node.js package manager, npm.

npm i mocha chai chai-http sinon mocha-junit-reporter istanbul nyc --save-dev        

This command will install all of the required libraries as dev dependencies in your project.

Mocha

Mocha is a popular JavaScript testing framework that runs on Node.js and the browser. It provides a clean syntax for writing tests and supports many features, including asynchronous testing, test reporting, and hooks for running pre- and post-test scripts.

Usage

To use Mocha, you need to write test files that follow a specific syntax. A test file should have one or more describe blocks that group related tests together. Within each described block, there should be one or more blocks that define individual test cases.

Here's an example of a Mocha test file for a REST API:

const assert = require('chai').assert
const app = require('../app');


describe('Blog API', function() {
  it('should return all blog posts', function(done) {
    chai.request(app)
      .get('/api/posts')
      .end(function(err, res) {
        assert.equal(res.status, 200);
        assert.isArray(res.body);
        done();
      });
  });
});        

In this example, we use to describe to group the tests for the Blog API together. We then use it to define a test case that verifies that the API returns all blog posts. We use chai. request() to send a GET request to the API and then use assert to check the response status and body.

Running Tests with Mocha

To run your tests with Mocha, you need to use the mocha command followed by the path to your test files:

mocha tests/**/*.js        

This command will run all the test files in the tests directory and its subdirectories that have a .js extension.

Chai

Chai is a popular assertion library that provides a set of functions for making assertions in your tests. It supports several styles of assertions, including assert, expect, and should.

Usage

Here's an example of how you can use Chai's assert style to make assertions in your tests:

const assert = require('chai').assert

describe('Blog API', function() {
  it('should return all blog posts', function(done) {
    chai.request(app)
      .get('/api/posts')
      .end(function(err, res) {
        assert.equal(res.status, 200);
        assert.isArray(res.body);
        done();
      });
  });
});        

In this example, we use Chai's assert function to make two assertions: that the response status is equal to 200 and that the response body is an array.

Mocha JUnit Reporter

Mocha JUnit Reporter is a library used for generating JUnit-style XML reports for Mocha test results. This library is useful when you need to integrate your tests with tools that support JUnit-style XML reports, such as Jenkins or CircleCI.

To use Mocha JUnit Reporter, you need to install it using npm:

npm install mocha-junit-reporter --save-dev        

After installation, you need to add the reporter to the Mocha command using the --reporter option:

mocha test/**/*.js --reporter mocha-junit-reporter --reporter-options mochaFile=./test-results.xml        

This will generate an XML report file in the root directory of your project named test-results.xml. The generated report file can be used to analyze test results.

Istanbul

Istanbul is a code coverage tool for JavaScript. It allows you to measure how much of your codebase is covered by your tests. You can use Istanbul to identify areas of your code that are not being tested and to optimize your test suite for better code coverage.

To use Istanbul, you need to install it using npm:

npm install nyc --save-dev        

After installation, you need to modify your package.json file to add the following configuration:

"scripts": {
  "test": "nyc mocha test/**/*.js"
},
"nyc": {
  "reporter": [
    "lcov",
    "text-summary"
  ],
  "exclude": [
    "test/**/*"
  ],
  "all": true
}        

This will configure Istanbul to run your tests using Mocha and generate coverage reports in both lcov and text-summary formats. It also excludes test files from coverage reporting and sets all options to true, which means Istanbul will collect coverage information for all files, not just the ones executed during tests.

To run your tests with Istanbul, use the following command:

npm test        

After running the tests, Istanbul will generate a coverage report that can be viewed in the browser by opening coverage/index.html.

NYC

NYC is a command-line interface for Istanbul. It provides additional functionality, such as a watch mode for automatically running tests when changes are made to the codebase.

To use NYC, you need to install it using npm:

npm install nyc --save-dev        

After installation, you can use NYC to run your tests with coverage using the following command:

nyc mocha test/**/*.js        

This will generate a coverage report that can be viewed in the browser by opening coverage/index.html.

NYC also provides a watch mode, which automatically runs tests when changes are made to the codebase. To use the watch mode, use the following command:

nyc --watch --reporter lcov --reporter text-summary mocha test/**/*.js        

This will run your tests in watch mode and generate coverage reports in both lcov and text-summary formats.

Conclusion

In conclusion, testing is an essential part of developing any application, and Node.js Rest API is no exception. Mocha, Chai, Chai-HTTP, and Sinon are powerful testing libraries that allow developers to write comprehensive and robust test suites. Mocha JUnit Reporter, Istanbul, and NYC are useful tools for generating reports and measuring code coverage. By using these libraries and tools, developers can ensure that their Node.js Rest API is reliable, efficient, and secure.