File download verification in Cypress - Test Execution Trace

Test Overview

This test checks if a file download starts correctly when the user clicks the download button. It verifies the file exists in the download folder after the click.

Test Code - Cypress

Cypress

describe('File Download Verification', () => {
  it('should download the file when clicking the download button', () => {
    cy.visit('https://example.com/download-page');
    const downloadsFolder = Cypress.config('downloadsFolder');

    cy.get('#download-btn').click();

    const downloadedFileName = 'sample.pdf';
    const downloadedFilePath = `${downloadsFolder}/${downloadedFileName}`;

    cy.readFile(downloadedFilePath, { timeout: 15000 }).should('exist');
  });
});

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test runner initialized, no browser opened yet	—	PASS
2	Browser opens and navigates to 'https://example.com/download-page'	Browser shows the download page with a download button having id 'download-btn'	—	PASS
3	Finds the download button using selector '#download-btn'	Download button is visible and enabled	Check that element '#download-btn' exists	PASS
4	Clicks the download button	Browser initiates file download of 'sample.pdf'	—	PASS
5	Reads the downloaded file 'sample.pdf' from the downloads folder	File 'sample.pdf' is expected to be present in the downloads folder	Verify file exists at path `${downloadsFolder}/sample.pdf`	PASS

Failure Scenario

Failing Condition: The file 'sample.pdf' does not appear in the downloads folder within the timeout period

Execution Trace Quiz - 3 Questions

What does the test verify after clicking the download button?

A The page URL changes

B The button changes color

C The file exists in the downloads folder

D An alert pops up

Key Result

Always verify file downloads by checking the actual file presence in the downloads folder with a timeout to handle download delays.

Practice

1. What is the main purpose of file download verification in Cypress testing?

easy

A. To speed up the test execution time

B. To ensure the downloaded file is correct and complete

C. To check the website's loading speed

D. To verify the page layout after download

Solution

1. Step 1: Understand file download verification

   File download verification checks if the file users get is the right one and fully downloaded.

2. Step 2: Identify the main goal

   The goal is to confirm the file content and completeness, not speed or layout.

3. Final Answer:

   To ensure the downloaded file is correct and complete -> Option B

4. Quick Check:

   File correctness = B [OK]

Hint: File download verification checks file correctness, not speed [OK]

Common Mistakes:

• Confusing download verification with page speed testing
• Thinking it checks page layout after download
• Assuming it speeds up tests

2. Which Cypress command is used to read the contents of a downloaded file for verification?

easy

A. cy.readFile()

B. cy.getFile()

C. cy.downloadFile()

D. cy.checkFile()

Solution

1. Step 1: Identify commands related to file handling

   cy.downloadFile() downloads files, cy.readFile() reads file contents.

2. Step 2: Choose the command to read file contents

   To verify file content, cy.readFile() is used, not cy.downloadFile().

3. Final Answer:

   cy.readFile() -> Option A

4. Quick Check:

   Read file = cy.readFile() = A [OK]

Hint: Use cy.readFile() to check file content after download [OK]

Common Mistakes:

• Using cy.downloadFile() to read file content
• Assuming cy.getFile() exists
• Confusing cy.checkFile() with real commands

3. Given the code snippet:

cy.downloadFile('https://example.com/report.pdf', 'cypress/downloads', 'report.pdf')
  .then(() => {
    cy.readFile('cypress/downloads/report.pdf').should('exist')
  })

What will this test verify?

medium

A. That the downloads folder is empty before download

B. That the file 'report.pdf' is empty

C. That the URL 'https://example.com/report.pdf' is reachable

D. That the file 'report.pdf' exists in the downloads folder after download

Solution

1. Step 1: Analyze the downloadFile command

   The command downloads 'report.pdf' to 'cypress/downloads'.

2. Step 2: Analyze the readFile assertion

   It checks if 'report.pdf' exists in the downloads folder after download.

3. Final Answer:

   That the file 'report.pdf' exists in the downloads folder after download -> Option D

4. Quick Check:

   File existence check = D [OK]

Hint: Check file existence with cy.readFile().should('exist') [OK]

Common Mistakes:

• Assuming it checks file content or emptiness
• Thinking it tests URL reachability
• Confusing pre-download folder state with post-download check

4. Identify the error in this Cypress test code for file download verification:

cy.downloadFile('https://example.com/data.csv', 'cypress/downloads', 'data.csv')
cy.readFile('cypress/downloads/data.csv').should('contain', 'Name, Age')

medium

A. Wrong assertion method; should use 'exist' instead of 'contain'

B. Incorrect file path in readFile command

C. Missing chaining or waiting for download to complete before reading file

D. cy.downloadFile does not exist in Cypress

Solution

1. Step 1: Check command sequence and chaining

   The download and readFile commands run separately without waiting for download to finish.

2. Step 2: Identify the need for chaining or waiting

   Without chaining or waiting, readFile may run before download completes, causing test failure.

3. Final Answer:

   Missing chaining or waiting for download to complete before reading file -> Option C

4. Quick Check:

   Wait for download before readFile = C [OK]

Hint: Chain commands or wait to ensure download finishes before reading [OK]

Common Mistakes:

• Running readFile immediately without waiting
• Assuming cy.downloadFile is not a valid command
• Using wrong assertion method for content check

5. You want to verify that a downloaded CSV file contains the header 'ID, Name, Email' and is not empty. Which Cypress test code correctly achieves this?

hard

A. cy.downloadFile('https://example.com/users.csv', 'cypress/downloads', 'users.csv')
.then(() => {
cy.readFile('cypress/downloads/users.csv').should('contain', 'ID, Name, Email').and('not.be.empty')
})

B. cy.readFile('cypress/downloads/users.csv').should('contain', 'ID, Name, Email')
cy.downloadFile('https://example.com/users.csv', 'cypress/downloads', 'users.csv')

C. cy.downloadFile('https://example.com/users.csv', 'cypress/downloads', 'users.csv')
cy.readFile('cypress/downloads/users.csv').should('exist')

D. cy.downloadFile('https://example.com/users.csv', 'cypress/downloads', 'users.csv')
.then(() => {
cy.readFile('cypress/downloads/users.csv').should('be.empty')
})

Solution

1. Step 1: Ensure download completes before reading file

   cy.downloadFile('https://example.com/users.csv', 'cypress/downloads', 'users.csv') .then(() => { cy.readFile('cypress/downloads/users.csv').should('contain', 'ID, Name, Email').and('not.be.empty') }) chains .then() after downloadFile to wait for completion.

2. Step 2: Verify file contains header and is not empty

   cy.downloadFile('https://example.com/users.csv', 'cypress/downloads', 'users.csv') .then(() => { cy.readFile('cypress/downloads/users.csv').should('contain', 'ID, Name, Email').and('not.be.empty') }) uses should('contain', ...) and .and('not.be.empty') correctly to check content and non-empty file.

3. Final Answer:

   cy.downloadFile('https://example.com/users.csv', 'cypress/downloads', 'users.csv') .then(() => { cy.readFile('cypress/downloads/users.csv').should('contain', 'ID, Name, Email').and('not.be.empty') }) -> Option A

4. Quick Check:

   Chain download and readFile with content checks = A [OK]

Hint: Chain downloadFile with readFile and use should contain + not.be.empty [OK]

Common Mistakes:

• Not chaining download and readFile causing timing issues
• Checking file existence only without content validation
• Asserting file is empty instead of not empty