Cypress Integration in Next.js.

How to implement Cypress in NextJS

Cypress is a powerful end-to-end testing framework in addition it allows developers to write automated tests for web applications. Furthermore, It provides a user-friendly interface, a robust API, and excellent documentation that makes it easy to use for developers of all skill levels. On the other hand, Next.js is a popular server-side rendering framework for React that allows developers to build fast and scalable web applications.

In this blog post, we will explore how to use this testing library with Next.js to create automated tests for web applications. We will discuss the benefits of using this, how to set up a Next.js project with this, and how to write some common tests.

Benefits of Using Cypress with Next.js

It is a powerful tool for testing web applications, and Next.js is an excellent framework for building web applications. When used together, they offer several benefits, including:

• Fast and reliable tests: This testing library coupled with a user-friendly interface allows developers to write tests quickly and easily. It also offers a robust API that makes it easy to test complex web applications. Next.js, on the other hand, provides server-side rendering, which means that the initial load time for the web application is faster, resulting in faster tests.
• Easy setup: Setting up a Next.js project with this library is straightforward. There are several tutorials and guides available online that provide step-by-step instructions on how to set up a Next.js project with Cypress.
• Excellent documentation: In addition, This testing library offers excellent documentation that makes it easy to use for developers of all skill levels. Above all, The documentation provides examples, tutorials, and best practices for writing tests using this.
• Integration with CI/CD tools: This library can be integrated with several CI/CD tools such as Jenkins, Travis, and CircleCI, allowing developers to run tests automatically after each code deployment.

Some Recommendations While Testing Your Next.js App:

To minimize errors and conflicts when testing your Next.js app, follow these best practices:

1. Keep your code content as much as possible in pure React components
   Simple components that only accept props and output JSX are very easy to test using Component Tests. Keep as much of your logic as possible in these components.
2. Separation of Concerns should be maintained
   Each component should have a single purpose or focus. Tacking on behaviors or content to an existing component is tempting, but is usually better to refactor it into two or more smaller components.
3. Minimize your Next.js integration tests
   Using Next.js integrations like useRouter is convenient, but maybe not in every single component. Consider centralizing their usage into a subset of components or hooks, and supply needed features elsewhere by passing props and callbacks.
4. Use your Page Components as data wrappers
   It’s tempting to directly create page layouts and content within your Page Component JSX, but this can make them difficult to test due to the issues with data hooks and integrations called out above. Consider using a Page Component as a data wrapper that passes props to pure React components for layout and structure.

Setting up a Next.js Project with Cypress

To set up a Next.js project with Cypress, follow these steps:

To set up a Next.js project with Cypress, follow these steps:

npx create-next-app

Install Cypress using the following command:

npm i cypress --save-dev

Create a new folder called “cypress” in the root directory of the Next.js project.

Create a new file called “cypress.json” in the “cypress” folder with the following contents:

{
"baseUrl": "http://localhost:3000" 
}

This file tells the testing library the base URL of the Next.js project.

Create a new file called “index.js” in the “cypress/integration” folder with the following contents:

describe('Example Test', () => {
  it('should navigate to example page', () => {
    cy.visit('/example');
  });
});

This test navigates to the example page of the Next.js project.

Start the Next.js project using the following command:

npm run dev

Start the test runner using the following command:

npx cypress open

This command opens the Test Runner for Cypress, where you can run the test you created for example page.

Above all some common Tests for different types of components in Next.js Applications Using Cypress

Writing tests for Next.js applications using Cypress is likewise to writing tests for any other web application.

In addition, it provides a user-friendly interface and a robust API that makes it easy to write tests for complex web applications. In this section, we will discuss how to write tests for Next.js applications using this testing library.

One of the essential aspects of any web application is navigation. Next.js provides a powerful routing system that allows developers to create client-side and server-side routes easily. To test navigation in a Next.js application using this library, use the cy.visit() command to navigate to the different routes.

And, you can write assertions as well to check if the correct page has been loaded. For example, to test if the About page has been loaded correctly, use the following code:

describe('Navigation', () => {
  it('should navigate to the home page', () => {
    cy.visit('https://example.com');
    cy.contains('Home').click();
    cy.url().should('include', '/home');
  });

  it('should navigate to the about page', () => {
    cy.visit('https://example.com');
    cy.contains('About').click();
    cy.url().should('include', '/about');
  });

  it('should navigate to the contact page', () => {
    cy.visit('https://example.com');
    cy.contains('Contact').click();
    cy.url().should('include', '/contact');
  });
});

Forms are an essential part of most web applications, and testing them is crucial to ensure that they function correctly. To test forms in a Next.js application using this library, use the cy.get() command to locate form elements and the cy.type() command to simulate user input. For example, to test if a form is submitted correctly, use the following code:

describe('Form Submission', () => {
  it('should submit a form with valid data', () => {
    cy.visit('https://example.com/form')
    cy.get('#name').type('John Doe')
    cy.get('#email').type('john.doe@example.com')
    cy.get('#message').type('Hello, world!')
    cy.get('#submit').click()
    cy.contains('Thank you for submitting the form!').should('be.visible')
  })

  it('should display an error message with invalid data', () => {
    cy.visit('https://example.com/form')
    cy.get('#name').type('John Doe')
    cy.get('#email').type('invalidemail')
    cy.get('#message').type('Hello, world!')
    cy.get('#submit').click()
    cy.contains('Please enter a valid email address.').should('be.visible')
  })
})

Here, we’re testing two different scenarios:

• We use the cy.visit() command to visit the form page before filling in the form fields and clicking the submit button. Then, we use the cy.get() command to find the form fields by their IDs and use the cy.type() command to fill in the data.
• Finally, we use the cy.contains() command to check that the success message is displayed after submitting the form with valid data, and the error message is displayed after submitting the form with invalid data.
• This code navigates to a form page, fills out the form fields with test data, clicks the submit button, and checks if a success message is displayed on the page.

As Authentication is a crucial aspect of many web applications, and testing necessary to ensure that users can log in and access protected resources.

To test authentication here using Cypress, use the cy.request() command to make HTTP requests to the application’s API endpoints. For example, to test if a user can log in successfully, use the following code:

describe('Authentication', () => {
  it('should log in with valid credentials', () => {
    cy.visit('https://example.com/login')
    cy.get('#username').type('john.doe')
    cy.get('#password').type('password123')
    cy.get('#login').click()
    cy.url().should('include', '/dashboard')
  })

  it('should display an error message with invalid credentials', () => {
    cy.visit('https://example.com/login')
    cy.get('#username').type('john.doe')
    cy.get('#password').type('wrongpassword')
    cy.get('#login').click()
    cy.contains('Invalid username or password.').should('be.visible')
  })
})

Here, we’re testing two different scenarios:

• We use the cy.visit() command to visit the login page before filling in the username and password fields and clicking the login button.
• Then, we use the cy.get() command to find the username and password fields by their IDs and use the cy.type() command to fill in the data.
• Finally, we use the cy.contains() command to check that the error message is displayed after submitting the form with invalid credentials, and after that dashboard page is displayed after submitting the form with valid credentials.
• This test will ensure that the authentication process is working correctly and that the user is receiving the appropriate feedback.

This code makes a POST request to the /api/login endpoint with test user credentials and checks if the response contains an access token.

Collection of links of blogs I found for Cypress examples and cheatsheets:

• Some commonly used cypress commands.
• Cypress Assertions Cheat Sheet to check the state of the application.
• Cypress Cheat Sheet for Traversing DOM Elements.
• A Detailed Guide about Cypress .should() Command.
• Exception Handling In Cypress.
• Cypress Tips And Tricks With Examples And Best Practices.
• How to Handle Opening a New Tab in Cypress.
• Some Common Cypress Features.
• Cypress Viewports test with automation.
• To get element text for test in Cypress.
• Guide to counting the total number of elements on the page.
• A guide about Cypress Test Runner.

Some other blogs are:

• Next.js with material and tailwind.
• Shallow routing in next.js

In Conclusion

In this blog post, we have explored how to use Cypress with Next.js to create automated tests for web applications. We have discussed the benefits of using this testing library, how to set up this with the Next.js project, and how to write tests for Next.js applications using this great library. By using Cypress with Next.js, developers can create fast and reliable automated tests that help ensure the quality of their web applications. For more information, you can check:

Cypress Official documentation

Next.js official documentation