Setup

On first use, read setup.md for integration guidelines.

When to Use

User needs E2E tests, component tests, or API tests with Cypress. Agent writes tests, debugs flaky specs, configures CI/CD, and creates custom commands.

Architecture

Project tests live in the standard Cypress structure:

cypress/
├── e2e/              # E2E test specs
├── component/        # Component tests (if enabled)
├── fixtures/         # Test data JSON files
├── support/
│   ├── commands.ts   # Custom commands
│   ├── e2e.ts        # E2E support file
│   └── component.ts  # Component support file
└── downloads/        # Downloaded files during tests
cypress.config.ts     # Main configuration

Quick Reference

Core Rules

1. Selectors: data-testid First

// ✅ Resilient — survives refactors
cy.get('[data-testid="submit-btn"]')
cy.get('[data-cy="user-list"]')
// ❌ Fragile — breaks on style/structure changes
cy.get('.btn-primary.submit')
cy.get('#root > div > form > button:nth-child(3)')
cy.get('button').contains('Submit')  // OK for text, not structure

Priority order: data-testid > data-cy > aria-* > text content > CSS selectors.

2. Never Use Fixed Waits

// ❌ Flaky and slow
cy.wait(3000)
cy.get('.loader').should('exist')
cy.wait(2000)
// ✅ Wait for actual state
cy.get('.loader').should('not.exist')
cy.get('[data-testid="results"]').should('be.visible')
cy.intercept('GET', '/api/users').as('getUsers')
cy.wait('@getUsers')

3. Intercept Network Requests

// Setup intercepts BEFORE triggering actions
cy.intercept('POST', '/api/login', { statusCode: 200, body: { token: 'abc' } }).as('login')
cy.get('[data-testid="login-btn"]').click()
cy.wait('@login')

4. One Assertion Focus per Test

// ✅ Clear failure message
it('shows error on invalid email', () => {
  cy.get('[data-testid="email"]').type('invalid')
  cy.get('[data-testid="submit"]').click()
  cy.get('[data-testid="email-error"]').should('contain', 'Valid email required')
})
// ❌ Multiple concerns — unclear which failed
it('validates the entire form', () => {
  // Tests 5 different validation rules
})

5. Commands for Repeated Actions

// cypress/support/commands.ts
Cypress.Commands.add('login', (email: string, password: string) => {
  cy.session([email, password], () => {
    cy.visit('/login')
    cy.get('[data-testid="email"]').type(email)
    cy.get('[data-testid="password"]').type(password)
    cy.get('[data-testid="submit"]').click()
    cy.url().should('include', '/dashboard')
  })
})
// Usage
cy.login('user@example.com', 'password123')

6. Fixtures for Test Data

// cypress/fixtures/user.json
{
  "validUser": { "email": "test@example.com", "password": "Test123!" },
  "adminUser": { "email": "admin@example.com", "password": "Admin123!" }
}

cy.fixture('user').then((users) => {
  cy.login(users.validUser.email, users.validUser.password)
})

7. Isolation: Reset State Before Tests

beforeEach(() => {
  cy.intercept('GET', '/api/notifications', { body: [] })
  cy.clearCookies()
  cy.clearLocalStorage()
  // Or: cy.task('db:seed') if using database reset
})

Common Traps

Debugging

Time Travel

Pause and Step

cy.get('[data-testid="item"]').then(($el) => {
  debugger  // Opens DevTools
})
// Or
cy.pause()  // Pause execution, step manually

Console Debugging

cy.get('[data-testid="items"]')
  .should('have.length.gt', 0)
  .then(($items) => {
    console.log('Found items:', $items.length)
  })

Configuration

cypress.config.ts Essentials

import { defineConfig } from 'cypress'
export default defineConfig({
  e2e: {
    baseUrl: 'http://localhost:3000',
    viewportWidth: 1280,
    viewportHeight: 720,
    defaultCommandTimeout: 10000,
    requestTimeout: 10000,
    retries: { runMode: 2, openMode: 0 },
    video: false,  // Enable for CI debugging
    screenshotOnRunFailure: true,
    setupNodeEvents(on, config) {
      // Plugins here
    },
  },
  component: {
    devServer: {
      framework: 'react',  // or 'vue', 'angular', etc.
      bundler: 'vite',     // or 'webpack'
    },
  },
})

TypeScript Support

// cypress/support/commands.ts
declare global {
  namespace Cypress {
    interface Chainable {
      login(email: string, password: string): Chainable
      getByTestId(testId: string): Chainable>
    }
  }
}
Cypress.Commands.add('getByTestId', (testId: string) => {
  return cy.get([data-testid="${testId}"])
})

Running Tests

External Endpoints

This skill does not call external APIs. Cypress runs entirely locally or in your own CI environment.

Security & Privacy

Data that stays local:

• All test code and fixtures remain in project directory
• Cypress runs locally or in your own CI environment

This skill does NOT:

• Send data to external services
• Require API keys or authentication
• Access files outside project directory

Note: Cypress Cloud (optional, paid) can receive test results if configured with CYPRESS_RECORD_KEY. This skill does not configure or recommend it.

Related Skills

• playwright — alternative E2E framework
• typescript — TypeScript best practices
• javascript — JS fundamentals and patterns
• react — React component testing

Feedback

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