Task command for Node operations in Cypress - Framework Patterns

Framework Mode - Task command for Node operations

Folder Structure

cypress/
├── e2e/
│   └── example.cy.js          # Test specs using Cypress commands and tasks
├── support/
│   ├── commands.js            # Custom Cypress commands
│   └── e2e.js                 # Support file loaded before tests, registers tasks
├── plugins/                  # (Optional legacy folder, replaced by cypress.config.js in Cypress 10+)
cypress.config.js            # Main Cypress configuration file with task registration
package.json                 # Project dependencies and scripts

Test Framework Layers

• Test Specs (cypress/e2e/): Write your tests here. Use cy.task() to call Node operations.
• Support Layer (cypress/support/): Define reusable commands and setup code. Import commands and register event listeners.
• Node Task Layer (cypress.config.js): Register task event handlers that run Node.js code outside the browser context.
• Utilities: Helper functions or modules imported by tasks for file operations, API calls, or other Node tasks.
• Configuration: Central place to manage environment variables, browser settings, and task definitions.

Configuration Patterns

Use cypress.config.js to register tasks and manage environment variables.

import { defineConfig } from 'cypress'

export default defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
      on('task', {
        readFile(filename) {
          const fs = require('fs')
          return fs.readFileSync(filename, 'utf8')
        },
        log(message) {
          console.log(message)
          return null
        }
      })
      return config
    },
    env: {
      apiUrl: 'https://api.example.com',
      userEmail: '[e-mail]'
    },
    baseUrl: 'https://app.example.com'
  }
})

Access environment variables in tests with Cypress.env('apiUrl').

Test Reporting and CI/CD Integration

• Use built-in Cypress reporters or plugins like mochawesome for detailed HTML and JSON reports.
• Configure package.json scripts to run tests headlessly in CI environments:

"scripts": {
  "test": "cypress run"
}

• Integrate with CI tools (GitHub Actions, Jenkins, GitLab CI) to run tests on pull requests or merges.
• Use cy.task() to perform Node operations like cleaning test data or generating reports during CI runs.

Best Practices

• Keep Node tasks simple and focused: Each task should do one thing, like reading a file or clearing a database.
• Return serializable data: Tasks must return data that can be sent back to the browser context (strings, objects, arrays).
• Use cy.task() for operations not possible in the browser: File system access, database queries, or external API calls.
• Register tasks in cypress.config.js: Centralize task definitions for easier maintenance.
• Secure sensitive data: Use environment variables and avoid hardcoding secrets in tasks or tests.

Self Check

Where in this framework structure would you add a new Node task to delete temporary test files?

Key Result

Use cy.task() registered in cypress.config.js to run Node operations from Cypress tests.

Practice

1. What is the main purpose of the cy.task() command in Cypress?

easy

A. To run Node.js code during Cypress tests

B. To select elements on the webpage

C. To assert values in the DOM

D. To take screenshots automatically

Solution

1. Step 1: Understand the role of cy.task()

   The cy.task() command allows Cypress tests to execute Node.js code outside the browser environment.

2. Step 2: Differentiate from other commands

   Commands like selecting elements or assertions happen inside the browser, but cy.task() runs backend code for tasks like file access.

3. Final Answer:

   To run Node.js code during Cypress tests -> Option A

4. Quick Check:

   Node code execution = A [OK]

Hint: Remember: cy.task() runs backend Node code [OK]

Common Mistakes:

• Confusing cy.task() with DOM commands
• Thinking cy.task() runs in the browser
• Assuming cy.task() is for assertions

2. Which of the following is the correct way to call a task named readFile in a Cypress test?

easy

A. cy.command('readFile')

B. cy.readFile('readFile')

C. cy.task('readFile')

D. cy.nodeTask('readFile')

Solution

1. Step 1: Recall the syntax for calling tasks

   In Cypress, tasks defined in the config are called using cy.task('taskName').

2. Step 2: Verify other options

   cy.readFile is a different command for reading files in the browser context, not tasks. The others are invalid commands.

3. Final Answer:

   cy.task('readFile') -> Option C

4. Quick Check:

   Use cy.task() to call tasks [OK]

Hint: Use cy.task('name') to run tasks [OK]

Common Mistakes:

• Using cy.readFile instead of cy.task
• Trying non-existent commands like cy.nodeTask
• Passing task name without quotes

3. Given this task definition in cypress.config.js:

tasks: {
  getEnv() {
    return process.env.NODE_ENV
  }
}

What will this test print?

cy.task('getEnv').then(env => {
  cy.log(env)
})

medium

A. It throws a syntax error

B. It logs an empty string

C. It logs 'undefined'

D. It logs the current NODE_ENV value

Solution

1. Step 1: Understand the task function

   The task getEnv returns the value of process.env.NODE_ENV, which is the environment mode (like 'development' or 'production').

2. Step 2: Analyze the test code

   The test calls cy.task('getEnv') and logs the returned value, so it will print the current environment string.

3. Final Answer:

   It logs the current NODE_ENV value -> Option D

4. Quick Check:

   Task returns env string = B [OK]

Hint: Tasks return Node values; cy.task() logs them [OK]

Common Mistakes:

• Assuming task runs in browser context
• Expecting syntax errors from valid code
• Thinking environment variables are empty by default

4. What is wrong with this task definition in cypress.config.js?

tasks: {
  readFile(path) {
    const fs = require('fs')
    return fs.readFileSync(path, 'utf8')
  }
}

When called as cy.task('readFile', 'data.txt'), it throws an error.

medium

A. The task function must return a Promise or value, but readFileSync is synchronous

B. The task should be defined as an async function returning a Promise

C. Tasks cannot accept arguments

D. The require statement is not allowed inside tasks

Solution

1. Step 1: Understand task function requirements

   Cypress tasks should return a value or a Promise. Using synchronous readFileSync is allowed but can cause blocking issues.

2. Step 2: Identify best practice for async operations

   To avoid errors and improve performance, tasks reading files should be async and return a Promise, e.g., using fs.promises.readFile.

3. Step 3: Analyze the error cause

   The error likely occurs because Cypress expects a Promise for async tasks, so defining the task as async fixes it.

4. Final Answer:

   The task should be defined as an async function returning a Promise -> Option B

5. Quick Check:

   Async tasks return Promises = D [OK]

Hint: Use async functions for tasks doing file I/O [OK]

Common Mistakes:

• Thinking synchronous code always works in tasks
• Believing require is disallowed inside tasks
• Assuming tasks cannot take arguments

5. You want to create a Cypress task that reads a JSON file and returns only the keys of the top-level object. Which task definition is correct?

hard

A. async readKeys(file) {
const fs = require('fs').promises
const data = await fs.readFile(file, 'utf8')
return Object.keys(JSON.parse(data))
}

B. readKeys(file) {
const fs = require('fs')
const data = fs.readFileSync(file, 'utf8')
return JSON.parse(data).keys()
}

C. async readKeys(file) {
const fs = require('fs')
const data = await fs.readFile(file, 'utf8')
return Object.keys(data)
}

D. readKeys(file) {
const fs = require('fs')
const data = fs.readFileSync(file, 'utf8')
return Object.keys(data)
}

Solution

1. Step 1: Read file asynchronously and parse JSON

   async readKeys(file) { const fs = require('fs').promises const data = await fs.readFile(file, 'utf8') return Object.keys(JSON.parse(data)) } correctly uses fs.promises.readFile with await to read the file asynchronously, then parses JSON.

2. Step 2: Extract keys from parsed object

   It returns Object.keys() of the parsed JSON, which gives the top-level keys as required.

3. Step 3: Identify errors in other options

   readKeys(file) { const fs = require('fs') const data = fs.readFileSync(file, 'utf8') return JSON.parse(data).keys() } incorrectly calls .keys() on the parsed object (should use Object.keys()). Options C and D try to get keys from raw string data, which is incorrect.

4. Final Answer:

   async readKeys(file) { const fs = require('fs').promises const data = await fs.readFile(file, 'utf8') return Object.keys(JSON.parse(data)) } -> Option A

5. Quick Check:

   Async read + JSON parse + Object.keys = A [OK]

Hint: Parse JSON first, then get keys with Object.keys() [OK]

Common Mistakes:

• Calling .keys() on object instead of Object.keys()
• Trying to get keys from raw string data
• Using synchronous read without async/await properly