expressjsHow can I test my Express.js application?

Testing an Express.js application can be done using a variety of tools.

The most popular way is to use the supertest library. This library allows you to write test cases that make HTTP requests to your application and assert that the response is correct.

For example, with the following code you can test an endpoint that returns a JSON response:

const request = require('supertest');
const app = require('./app');

describe('GET /api/users', () => {
    it('should return a list of users', (done) => {
        request(app)
            .get('/api/users')
            .expect('Content-Type', /json/)
            .expect(200)
            .end((err, res) => {
                if (err) return done(err);
                expect(res.body).to.be.an('array');
                done();
            });
    });
});

The code above:

• Requires the supertest library and the application.
• Describes a test case for the endpoint GET /api/users.
• Makes a request to the endpoint with request(app).get('/api/users').
• Asserts that the response has the correct Content-Type and status code.
• Asserts that the response body is an array.

Other popular tools for testing Express applications are mocha, chai and sinon.

Helpful links

• supertest
• mocha
• chai
• sinon

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