Reading file contents in Cypress - Cheat Sheet & Quick Revision

Recall & Review

beginner

What Cypress command is used to read the contents of a file?

The cy.readFile() command is used to read the contents of a file in Cypress.

beginner

How do you assert that a file contains specific text using Cypress?

Use cy.readFile('path/to/file').should('contain', 'expected text') to check if the file contains the expected text.

beginner

What file path should you use in cy.readFile() to read a file inside the cypress/fixtures folder?

You can use a relative path like cypress/fixtures/filename.txt or just filename.txt if the default folder is set.

intermediate

Can cy.readFile() read JSON files and automatically parse them?

Yes, if you read a JSON file with cy.readFile('file.json'), Cypress automatically parses it into a JavaScript object.

intermediate

What happens if cy.readFile() tries to read a file that does not exist?

The test will fail with an error indicating the file was not found. You should ensure the file path is correct before reading.

Which Cypress command reads the contents of a file?

A cy.getFile()

B cy.readFile()

C cy.loadFile()

D cy.openFile()

cy.readFile() is the correct command to read file contents in Cypress.

How do you check if a file contains the text 'Hello World' in Cypress?

A cy.readFile('file.txt').should('contain', 'Hello World')

B cy.readFile('file.txt').should('have.text', 'Hello World')

C cy.get('file.txt').should('contain', 'Hello World')

D cy.read('file.txt').should('contain', 'Hello World')

Use cy.readFile() with should('contain', ...) to assert file content.

If you read a JSON file with cy.readFile(), what type of data do you get?

A A JavaScript object parsed from JSON

B A string with JSON text

C An array of bytes

D A file stream

Cypress automatically parses JSON files into JavaScript objects.

Where should test files be placed to be read easily with relative paths in Cypress?

A cypress/plugins

B cypress/support

C cypress/integration

D cypress/fixtures

The cypress/fixtures folder is the default location for test data files.

What happens if cy.readFile() tries to read a missing file?

A It returns an empty string

B It creates a new empty file

C It throws an error and fails the test

D It skips the test silently

Reading a non-existent file causes the test to fail with an error.

Explain how to read a text file and verify it contains a specific phrase using Cypress.

Think about reading the file first, then checking its content.

Describe what happens when you read a JSON file with cy.readFile() in Cypress.

Consider how JSON data is handled differently than plain text.

Practice

1. What is the primary purpose of cy.readFile() in Cypress testing?

easy

A. To read the contents of a file during a test

B. To write data to a file during a test

C. To delete a file before running tests

D. To upload a file to the server

Solution

1. Step 1: Understand the function name

   cy.readFile() suggests reading a file, not writing or deleting.

2. Step 2: Recall Cypress documentation

   This command reads file contents so tests can verify data inside files.

3. Final Answer:

   To read the contents of a file during a test -> Option A

4. Quick Check:

   cy.readFile() reads file contents [OK]

Hint: Remember: readFile reads, writeFile writes [OK]

Common Mistakes:

• Confusing readFile with writeFile
• Thinking it uploads files
• Assuming it deletes files

2. Which of the following is the correct syntax to read a JSON file named data.json using Cypress?

easy

A. cy.readFile('data.json', 'utf8')

B. cy.readFile('data.json').then((content) => { /* use content */ })

C. cy.readFile('data.json').catch((content) => { /* use content */ })

D. cy.readFile('data.json').write((content) => { /* use content */ })

Solution

1. Step 1: Identify correct method chaining

   Using then() after cy.readFile() is correct to access file content.

2. Step 2: Check other options

   catch() is for errors, not normal reading; write() is invalid here; passing 'utf8' alone is incomplete.

3. Final Answer:

   cy.readFile('data.json').then((content) => { /* use content */ }) -> Option B

4. Quick Check:

   Use then() to handle readFile content [OK]

Hint: Use then() to access file content after readFile [OK]

Common Mistakes:

• Using catch() instead of then()
• Trying to write after readFile
• Passing encoding without then()

3. Given the code below, what will be logged to the console if example.txt contains the text "Hello Cypress"?

cy.readFile('example.txt').then((text) => {
  console.log(text);
});

medium

A. Empty string

B. undefined

C. An error because readFile needs JSON

D. "Hello Cypress"

Solution

1. Step 1: Understand readFile behavior

   cy.readFile() reads file content as text by default if file is plain text.

2. Step 2: Check the file content

   The file contains "Hello Cypress", so the callback receives this string and logs it.

3. Final Answer:

   "Hello Cypress" -> Option D

4. Quick Check:

   readFile logs file text content [OK]

Hint: readFile returns file content as string for text files [OK]

Common Mistakes:

• Assuming readFile only works with JSON
• Expecting undefined instead of content
• Thinking it throws error for text files

4. Identify the error in the following Cypress code snippet that tries to read a file and assert its content:

cy.readFile('config.json').then((data) => {
  expect(data).to.equal('config');
});

medium

A. Incorrect file path syntax

B. Missing catch() to handle errors

C. Using to.equal() instead of to.deep.equal() for object comparison

D. readFile cannot be used with JSON files

Solution

1. Step 1: Understand data type returned by readFile

   Reading a JSON file returns an object, not a string.

2. Step 2: Check assertion method

   to.equal() checks strict equality, which fails for objects; to.deep.equal() is needed for object content comparison.

3. Final Answer:

   Using to.equal() instead of to.deep.equal() for object comparison -> Option C

4. Quick Check:

   Use deep.equal for object assertions [OK]

Hint: Use deep.equal for objects, equal for primitives [OK]

Common Mistakes:

• Using to.equal() for objects
• Ignoring error handling
• Assuming readFile can't read JSON

5. You want to verify that a text file notes.txt contains the word "important" anywhere in its content using Cypress. Which code snippet correctly performs this check?

hard

A. cy.readFile('notes.txt').then((text) => { expect(text.includes('important')).to.be.true; })

B. cy.readFile('notes.txt').should('contain', 'important')

C. cy.readFile('notes.txt').then((text) => { expect(text).to.equal('important'); })

D. cy.readFile('notes.txt').then((text) => { expect(text).to.have.property('important'); })

Solution

1. Step 1: Understand file content check

   We want to check if the word "important" is anywhere in the text, so we need to check substring presence.

2. Step 2: Evaluate options

   cy.readFile('notes.txt').then((text) => { expect(text.includes('important')).to.be.true; }) uses includes() and asserts true, which is correct. cy.readFile('notes.txt').should('contain', 'important') is invalid because should('contain') is for DOM elements, not file content. cy.readFile('notes.txt').then((text) => { expect(text).to.equal('important'); }) checks exact equality, which is wrong. cy.readFile('notes.txt').then((text) => { expect(text).to.have.property('important'); }) wrongly uses to.have.property() on a string.

3. Final Answer:

   cy.readFile('notes.txt').then((text) => { expect(text.includes('important')).to.be.true; }) -> Option A

4. Quick Check:

   Use includes() to check substring in file text [OK]

Hint: Use includes() inside then() to check text content [OK]

Common Mistakes:

• Using should('contain') on file content
• Checking exact equality instead of substring
• Using property assertion on string