Writing to files (cy.writeFile) in Cypress - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Cypress test writing JSON to a file?

Consider the following Cypress test code that writes a JSON object to a file. What will be the content of the file output.json after this test runs?

Cypress

cy.writeFile('output.json', { name: 'Alice', age: 30 })

A

{
  "name": "Alice",
  "age": 30
}

B "{ name: 'Alice', age: 30 }"

C { name: 'Alice', age: 30 }

D ["name", "Alice", "age", 30]

💡 Hint

cy.writeFile serializes objects to JSON format by default.

cy.writeFile writes the JavaScript object as a JSON string to the file. So the file content will be a properly formatted JSON string with keys and values.

❓ assertion

intermediate

Which assertion correctly verifies the file content after writing?

After running cy.writeFile('data.txt', 'Hello World'), which Cypress assertion correctly checks that the file contains exactly 'Hello World'?

A cy.readFile('data.txt').should('equal', 'Hello World')

B cy.readFile('data.txt').should('contain', 'Hello World!')

C cy.readFile('data.txt').should('include', 'hello world')

D cy.readFile('data.txt').should('eq', 'Hello World')

💡 Hint

Use the exact string match assertion.

The correct assertion is 'eq' to check exact equality. 'contain' and 'include' are for partial matches and case sensitive. 'equal' is not a valid Cypress assertion keyword.

🔧 Debug

advanced

Why does this cy.writeFile command fail with a TypeError?

Examine the code below. Why does it cause a TypeError during test execution?

const data = new Map([['key', 'value']]);
cy.writeFile('map.json', data);

Cypress

const data = new Map([['key', 'value']]);
cy.writeFile('map.json', data);

A cy.writeFile requires a string, but data is a Map, causing a TypeError.

B The file path 'map.json' is invalid and causes a TypeError.

C Map objects cannot be serialized to JSON directly, causing a TypeError.

D The Map object is empty, so cy.writeFile throws a TypeError.

💡 Hint

Think about how JavaScript objects are converted to JSON.

Map objects are not directly serializable to JSON. cy.writeFile tries to convert the Map to JSON but fails, causing a TypeError.

🧠 Conceptual

advanced

What is the best practice for writing large JSON data to a file in Cypress?

You have a large JSON object to write to a file during a Cypress test. Which approach is best to ensure the test runs efficiently and the file is correctly written?

A Use cy.writeFile with the JSON object directly; Cypress handles serialization efficiently.

B Convert the JSON object to a string with JSON.stringify and then use cy.writeFile with the string.

C Split the JSON object into smaller parts and write multiple files with cy.writeFile.

D Write the JSON object to a file using Node.js fs module inside the test.

💡 Hint

Consider Cypress's built-in handling of objects in cy.writeFile.

cy.writeFile automatically serializes objects to JSON efficiently. Manually stringifying is unnecessary and can add complexity. Splitting files or using Node fs is not recommended inside Cypress tests.

❓ framework

expert

How to ensure cy.writeFile completes before next test step in Cypress?

In a Cypress test, you write data to a file using cy.writeFile. You want to make sure the file write finishes before continuing to the next command. Which code snippet correctly ensures this?

A cy.writeFile('file.txt', 'data'); cy.log('Write complete')

B cy.writeFile('file.txt', 'data').then(() => { cy.log('Write complete') })

C await cy.writeFile('file.txt', 'data'); cy.log('Write complete')

D cy.writeFile('file.txt', 'data').catch(() => { cy.log('Write failed') })

💡 Hint

Use Cypress command chaining to wait for completion.

Cypress commands are asynchronous and chained. Using .then() after cy.writeFile ensures the next step runs after the file write completes. Option B runs cy.log immediately without waiting. Option B is invalid because Cypress commands do not support await. Option B handles errors but does not guarantee sequencing.