Unit Testing in JavaScript Testing Complex Routes

Learning objective: By the end of this lesson, students will be able to write tests for more complex routes in Express.

Testing more complex routes

Since we have already seen how to test a simple route, let’s look at how we can test a more complex route in Express. We are still going to be working in the same file, test/app.test.js.

Let’s test a POST route. We already have a post route to /users provided in the starter code. Just like with our previous tests, we’ll use describe to group our tests and it to define each test.

// test/app.test.js

// Set up grouping for tests
describe('POST /users', () => {
    it('adds a new user to the list', (done) => {
        
    });
});

For this test we want to add a new user to the list of users. Before we can do that, we’ll need a new user to add. Create a mock user in your test function:

// test/app.test.js

describe('POST /users', () => {
    it('adds a new user to the list', (done) => {
        // Add in a new mock user
        const newUser = {
            name: 'John Smith',
            email: 'john@example.com',
            password: 'john123',
            phoneNumber: '9876543210'
        };
    });
});

With this newUser object created, we can now make a request to the server to add the new user. We will be using the same request method but this time we will be making a POST request.

// test/app.test.js

describe('POST /users', () => {
    it('adds a new user to the list', (done) => {
        const newUser = {
            name: 'John Smith',
            email: 'john@example.com',
            password: 'john123',
            phoneNumber: '9876543210'
        };
        // Make a POST request to the server
        request(app)
            .post('/users')
    });
});

Remember to always pass the request method to the app listener so that it can make requests to the server.

Now we need a way to send the newUser data to the server. Luckily, the request method has a method called send that we can use to send data to the server.

// test/app.test.js

describe('POST /users', () => {
    it('adds a new user to the list', (done) => {
        const newUser = {
            name: 'John Smith',
            email: 'john@example.com',
            password: 'john123',
            phoneNumber: '9876543210'
        };
        
        request(app)
            .post('/users')
            // Send the new user data to the server
            .send(newUser)
    });
});

After we have sent the data to the server it’s time to test. As with our other tests we want to make sure the response is a JSON object and the status code is 200.

// test/app.test.js

describe('POST /users', () => {
    it('adds a new user to the list', (done) => {
        const newUser = {
            name: 'John Smith',
            email: 'john@example.com',
            password: 'john123',
            phoneNumber: '9876543210'
        };
        
        request(app)
            .post('/users')
            .send(newUser)
            // Test to ensure that the response is a JSON object
            .expect('Content-Type', /json/)
            // Test to ensure that the status code is 200
            .expect(200)
    });
});

Just like with our test for the GET route, we will be using .end to end the test. This end method will take a callback function that will be used to check the response from the server.

// test/app.test.js

describe('POST /users', () => {
    it('adds a new user to the list', (done) => {
        const newUser = {
            name: 'John Smith',
            email: 'john@example.com',
            password: 'john123',
            phoneNumber: '9876543210'
        };
        
        request(app)
            .post('/users')
            .send(newUser)
            .expect('Content-Type', /json/)
            .expect(200)
            // Test the response from the server
            .end((err, res) => {
                if (err) return done(err);
                expect(res.body.user).to.be.an('object');
                expect(res.body.user).to.have.property('name', newUser.name);
                expect(res.body.user).to.have.property('email', newUser.email);
                done();
            });
    });
});

Now that we have our test for the POST route, we can run the tests to see if they pass.

npm test

Great work!

Mocha and Chai form a user-friendly combination for a testing framework and an assertion library. In our lessons, we’ve just begun to explore the capabilities of these powerful tools. The foundational knowledge gained here can be effectively applied to larger applications. For those interested in diving deeper, we recommend exploring their official documentation.

• Mocha
• Chai

These resources offer a wealth of information and advanced techniques that can significantly enhance your testing skills and understanding.