Task command for Node operations in Cypress - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a Cypress task that returns the current working directory.

Cypress

Cypress.Commands.add('getCwd', () => {
  return cy.task([1])
});

Drag options to blanks, or click blank then click option'

A'workingDir'

B'cwd'

C'currentDir'

D'getCwd'

Attempts:

3 left

💡 Hint

Common Mistakes

Using an incorrect task name that is not registered in plugins.

Forgetting to wrap the task name in quotes.

The task name 'cwd' is commonly used to get the current working directory in Cypress tasks.

2fill in blank

medium

Complete the code to register a Cypress task that reads a file asynchronously.

Cypress

module.exports = (on, config) => {
  on('task', {
    readFile([1]) {
      const fs = require('fs').promises;
      return fs.readFile(path, 'utf8');
    }
  });
};

Drag options to blanks, or click blank then click option'

Apath

BfilePath

Cfilename

Dfile

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name different from the variable used inside the function.

Not using async/await or promises for reading files.

The parameter name 'path' matches the variable used inside the function to read the file.

3fill in blank

hard

Fix the error in the Cypress task that writes data to a file.

Cypress

on('task', {
  writeFile([1]) {
    const fs = require('fs');
    return fs.writeFileSync(filePath, data);
  }
});

Drag options to blanks, or click blank then click option'

AfilePath

BfilePath, data

C{filePath, data}

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Passing parameters without destructuring causing undefined variables.

Using writeFileSync without proper parameters.

The function parameter should destructure an object with filePath and data to use both variables inside the function.

4fill in blank

hard

Fill both blanks to create a Cypress task that deletes a file and returns success status.

Cypress

on('task', {
  deleteFile([1]) {
    const fs = require('fs');
    try {
      fs.unlinkSync([2]);
      return true;
    } catch (err) {
      return false;
    }
  }
});

Drag options to blanks, or click blank then click option'

AfilePath

Bpath

Dfilename

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing runtime errors.

Not handling exceptions properly.

The parameter and the argument to unlinkSync must be the same variable 'filePath' to delete the correct file.

5fill in blank

hard

Fill all three blanks to define a Cypress task that lists files in a directory and filters by extension.

Cypress

on('task', {
  listFiles([1]) {
    const fs = require('fs');
    const files = fs.readdirSync([2]);
    return files.filter(file => file.endsWith([3]));
  }
});

Drag options to blanks, or click blank then click option'

AdirPath

Bdirectory

Dext

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing errors.

Not filtering files correctly by extension.

The parameter and argument for readdirSync should be 'dirPath', and the filter uses 'ext' to check file extensions.

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