Cypress 🤖

The team prefers using Cypress for end-to-end testing on their front-end applications. It is easy to set up, and it provides some modern features which are convenient while writing end-to-end tests.

Configuration

• The team uses Typescript when building JavaScript applications. After installing Cypress and Typescript, configure Cypress to use Typescript. A sample tsconfig.json file looks like below

  {
    "compilerOptions": {
      "target": "es5",
      "lib": ["es5", "dom"],
      "types": ["cypress"],
      "moduleResolution": "node",
      "resolveJsonModule": true
    },
    "include": [
      "**/*.ts"
    ],
    "files": [
      "./support/index.d.ts"
    ]
  }
  

• Some scripts should be added to the package.json file for easier usage of Cypress

  "scripts": {
    "cypress:open": "cypress open",
    "cypress:run": "cypress run"
  }
  

• Base URL must be specified in the cypress.json to avoid repetitive definition of base URL in each test.

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

Formatting

• Use soft-tabs with a two-space indent.
• Limit each line of code to fewer than 130 characters.
• End each file with a newline.

• Do not leave line breaks after context or describe blocks.

  describe('User authentication', () => {
  
    context('given valid user credentials', () => {
  
      it('redirects to the landing page', () => {})
    })
  })
  

  describe('User authentication', () => {
    context('given valid user credentials', () => {
      it('redirects to the landing page', () => {})
    })
  })
  

• Leave one line return around context and it blocks.

  describe('User authentication', () => {
    context('given valid user credentials', () => {
      it('redirects to the landing page', () => {
        ...
      })
      it('shows user menu', () => {
        ...
      })
    })
    context('given INVALID user credentials', () => {
      it('shows login error', () => {
        ...
      })
    })
  })
  

  describe('User authentication', () => {
    context('given valid user credentials', () => {
      it('redirects to the landing page', () => {
        ...
      })
  
      it('shows user menu', () => {
        ...
      })
    })
  
    context('given INVALID user credentials', () => {
      it('shows login error', () => {
        ...
      })
    })
  })
  

Naming

• Use camelCase for file names.

• Each test file name must have the suffix .spec to distinguish test files from source files.

  integration/
  ├── UserAuthentication/
  │   ├── login.spec.ts
  │   ├── signup.spec.ts
  ├── UserSearch/
  │   ├── searchByEmail.spec.ts
  support/
  ├── commands.ts/
  

  To enforce this rule a configuration should be added in the cypress.json file

  {
     "testFiles": ["**/*.spec.ts"]
  }
  

• Use describe to group tests using the file name for the description.

  // searchByEmail.spec.json
  
  describe('Search by email', () => {})
  

• Use context to describe testing preconditions. context block descriptions must always start with when or given, and be in the form of a sentence with proper grammar.

  it('redirects to landing page if user credentials are valid', () => {})
  

  context('given valid user credentials', () => {
    it('redirects to the landing page', () => {})
  })
  

• Do NOT prefix it block descriptions with should. Use the imperative tone instead.

  it('should redirect to landing page', () => {})
  

  it('redirects to the landing page', () => {})
  

Element selector

Avoid using highly brittle HTML selectors that are subject to change with target elements. Use data-test-id attributes to provide context to the selectors and insulate them from CSS or JS changes.

<div data-test-id="userProfile"></div>

Functions

Use ES6 arrow function for describe/context/it block

describe('User authentication', function() {
  context('given valid user credentials', function() {
    it('redirects to the landing page', function() {})
  })
})

describe('User authentication', () => {
  context('given valid user credentials', () => {
    it('redirects to the landing page', () => {})
  })
})

Stub HTTP requests/responses

From Cypress v6.0.0 a new command cy.intercept() has been added to stub HTTP requests and responses. This command can be used to specify HTTP fixtures as well.

cy.intercept('http://example.com/widgets', { fixture: 'widgets.json' })

All information about this command can be found in the documentation.

Custom commands

Cypress supports user-defined commands. Custom commands are beneficial for automating a workflow repeated in tests. It can significantly DRY-up tests.

If an application requires login on each page, then this can be made into a custom command

Cypress.Commands.add('login', () => {
  cy.visit('/login')
  cy.get('input[name=email]').type('[email protected]')
  cy.get('input[name=password]').type(`'password'{enter}`)
})

Then this command can be easily used in tests as cy.login(). When using typescript adding a custom command requires a TypeScript definitions file. More can be found in the documentation.