Cypress is a next generation front end testing tool built for the modern web
Cypress is a JavaScript-based end-to-end testing framework that runs tests directly inside the browser using a Node.js server process. Unlike Selenium-based tools that communicate with browsers through WebDriver, Cypress executes in the same run loop as your application, giving it native access to the DOM, window objects, and network layer. This architecture enables capabilities like synchronous command execution, automatic waiting, and direct inspection of application state.
The framework was built to address the pain points of traditional browser automation tools: flaky tests caused by timing issues, difficult debugging workflows, and slow feedback loops. Cypress automatically waits for DOM elements to exist and become actionable before executing commands, eliminating the need for manual sleep statements. When tests fail, developers can use time-travel debugging to step through each command and inspect the exact application state at that moment.
Cypress handles both end-to-end testing of full application flows and component testing of isolated UI elements. It's widely adopted by teams building React, Vue, and Angular applications who need reliable automated testing in CI/CD pipelines. The framework includes built-in assertion libraries (Chai, Sinon, jQuery), fixture management, screenshot/video capture, and network traffic control without requiring additional dependencies.
With over 6.5 million weekly downloads, Cypress has become a standard tool for frontend testing. It supports Chrome-family browsers, Firefox, and Edge, with tests written in standard JavaScript or TypeScript. The framework's developer experience focuses on fast iteration cycles with hot-reloading of tests and real-time result visualization in an interactive Test Runner interface.
// cypress/e2e/login.cy.js
describe('User Authentication', () => {
beforeEach(() => {
cy.visit('https://example.com/login');
cy.intercept('POST', '/api/auth/login', {
statusCode: 200,
body: {
token: 'mock-jwt-token',
user: { id: 1, email: 'test@example.com', name: 'Test User' }
}
}).as('loginRequest');
});
it('successfully logs in with valid credentials', () => {
cy.get('input[name="email"]').type('test@example.com');
cy.get('input[name="password"]').type('SecurePass123!');
cy.get('button[type="submit"]').click();
cy.wait('@loginRequest').its('request.body').should('deep.equal', {
email: 'test@example.com',
password: 'SecurePass123!'
});
cy.url().should('include', '/dashboard');
cy.get('[data-testid="user-greeting"]').should('contain', 'Test User');
cy.getCookie('auth_token').should('exist');
});
it('displays error message for invalid credentials', () => {
cy.intercept('POST', '/api/auth/login', {
statusCode: 401,
body: { error: 'Invalid credentials' }
}).as('failedLogin');
cy.get('input[name="email"]').type('wrong@example.com');
cy.get('input[name="password"]').type('wrongpass');
cy.get('button[type="submit"]').click();
cy.wait('@failedLogin');
cy.get('[role="alert"]').should('be.visible').and('contain', 'Invalid credentials');
cy.url().should('include', '/login');
});
it('validates required fields before submission', () => {
cy.get('button[type="submit"]').click();
cy.get('input[name="email"]:invalid').should('exist');
cy.get('input[name="password"]:invalid').should('exist');
cy.get('@loginRequest.all').should('have.length', 0);
});
});User authentication flows: Test complete login, registration, and password reset sequences including form validation, API calls, session management, and redirect behavior. Stub authentication endpoints to test success and error states without depending on live backend services.
E-commerce checkout processes: Automate testing of multi-step purchasing flows including product selection, cart management, payment form validation, and order confirmation. Mock payment gateway responses to verify handling of declined cards, timeouts, and successful transactions.
Component integration testing: Test individual React, Vue, or Angular components in isolation by mounting them in a real browser environment. Verify component props, event emissions, conditional rendering, and interaction with context providers or state management libraries.
API integration and data loading: Intercept and stub REST or GraphQL API calls to test loading states, error handling, empty data scenarios, and data transformation logic. Verify that UI correctly displays API responses and gracefully handles network failures.
Cross-browser regression testing: Run the same test suite across Chrome, Firefox, and Edge to catch browser-specific bugs. Execute tests against multiple viewport sizes to verify responsive design behavior and mobile-specific interactions.
npm install cypresspnpm add cypressbun add cypress