cy.viewport() for screen sizes in Cypress - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the viewport size after this Cypress command?

Consider the following Cypress test code snippet:

cy.viewport(1024, 768);

What will be the viewport width and height set by this command?

Cypress

cy.viewport(1024, 768);

A Width: 1024px, Height: 768px

B Width: 768px, Height: 1024px

C Width: 1024px, Height: 1024px

D Width: 768px, Height: 768px

💡 Hint

The first argument is width, the second is height.

The cy.viewport() command sets the browser's viewport size. The first parameter is width, the second is height, so cy.viewport(1024, 768) sets width to 1024 pixels and height to 768 pixels.

❓ assertion

intermediate

Which assertion correctly verifies the viewport size?

You want to check if the viewport width is 375 pixels after setting it with cy.viewport(375, 667). Which assertion is correct?

Cypress

cy.viewport(375, 667);
// Which assertion below correctly checks the width?

A cy.document().its('width').should('equal', 375);

B cy.window().its('innerWidth').should('equal', 375);

C cy.get('body').should('have.css', 'width', '375px');

D cy.viewport().should('have.property', 'width', 375);

💡 Hint

The window object holds the viewport size properties.

The window object's innerWidth property reflects the viewport width. Using cy.window().its('innerWidth') accesses this value for assertion. Other options either check wrong properties or use invalid commands.

🧠 Conceptual

advanced

What happens if you use cy.viewport() with a preset device name?

In Cypress, what does this command do?

cy.viewport('iphone-6');

Choose the correct explanation.

A Sets the viewport to the screen size of an iPhone 6 but does not change device pixel ratio or user agent.

B Sets the viewport to the exact screen size of an iPhone 6 including device pixel ratio and user agent.

C Sets the viewport to a random mobile device size similar to iPhone 6.

D Throws an error because device names are not supported in cy.viewport().

💡 Hint

Device presets set viewport size but do not emulate device pixel ratio or user agent.

Using cy.viewport('iphone-6') sets the viewport size to iPhone 6 dimensions (375x667) but does not emulate device pixel ratio or user agent string. It only changes viewport size.

🔧 Debug

advanced

Why does this viewport test fail?

Given this test:

cy.viewport(800, 600);
cy.window().its('innerWidth').should('equal', 600);

Why does the assertion fail?

A Because the viewport height is 600, so innerWidth should be 600.

B Because cy.viewport() does not change innerWidth property.

C Because the assertion syntax is incorrect.

D Because innerWidth is the width, so it should be 800, not 600.

💡 Hint

Remember which value is width and which is height in cy.viewport().

cy.viewport(800, 600) sets width to 800 and height to 600. innerWidth reflects the width, so expecting 600 causes the test to fail.

❓ framework

expert

How to test responsive design for multiple screen sizes efficiently in Cypress?

You want to run the same test on multiple screen sizes: 320x480, 768x1024, and 1280x720. Which approach is best to write this in Cypress?

A Use a loop inside the test to call cy.viewport() with each size and run assertions inside the loop.

B Write separate tests for each screen size with hardcoded cy.viewport() calls.

C Use Cypress custom commands to set viewport and call the test logic once per size using a data-driven approach.

D Set cy.viewport() once globally and rely on browser resizing manually.

💡 Hint

Think about reusability and clean test code.

Using custom commands and data-driven tests allows running the same test logic for multiple viewport sizes cleanly and efficiently. Loops inside tests can cause flaky behavior, and separate tests cause duplication.

Practice

1. What is the main purpose of using cy.viewport() in Cypress tests?

easy

A. To change the screen size and test responsive layouts

B. To select elements on the page

C. To wait for an element to appear

D. To take screenshots of the page

Solution

1. Step 1: Understand the function of cy.viewport()

   This command sets the browser's screen size to simulate different devices or resolutions.

2. Step 2: Identify the purpose in testing

   Changing screen size helps test how the website looks and behaves on various devices, ensuring responsive design works.

3. Final Answer:

   To change the screen size and test responsive layouts -> Option A

4. Quick Check:

   cy.viewport() changes screen size = D [OK]

Hint: Remember: viewport changes screen size for responsive tests [OK]

Common Mistakes:

• Confusing viewport with element selectors
• Thinking viewport waits for elements
• Assuming viewport takes screenshots

2. Which of the following is the correct syntax to set the viewport size to 1024 pixels wide and 768 pixels tall in Cypress?

easy

A. cy.viewport({width: 1024, height: 768});

B. cy.viewport(1024, 768);

C. cy.viewport('1024x768');

D. cy.setViewport(1024, 768);

Solution

1. Step 1: Recall the correct cy.viewport() syntax

   The command accepts width and height as two separate number arguments: cy.viewport(width, height).

2. Step 2: Check each option

   cy.viewport(1024, 768); uses two numbers correctly. cy.viewport('1024x768'); uses a string which is invalid. cy.viewport({width: 1024, height: 768}); uses an object which is not supported. cy.setViewport(1024, 768); uses a wrong command name.

3. Final Answer:

   cy.viewport(1024, 768); -> Option B

4. Quick Check:

   cy.viewport(width, height) = C [OK]

Hint: Use two numbers, not strings or objects, in cy.viewport() [OK]

Common Mistakes:

• Passing size as a string like '1024x768'
• Using an object instead of two numbers
• Typing wrong command name like cy.setViewport

3. What will be the viewport size after running this Cypress code?

cy.viewport('iphone-6');
cy.viewport(800, 600);

medium

A. 800 pixels wide and 600 pixels tall

B. iPhone 6 preset size

C. Default viewport size

D. Test will fail due to conflicting viewport commands

Solution

1. Step 1: Understand command order in Cypress

   Commands run in order. The last cy.viewport() call sets the final size.

2. Step 2: Analyze the code

   First sets viewport to iPhone 6 size, then immediately changes it to 800x600 pixels.

3. Final Answer:

   800 pixels wide and 600 pixels tall -> Option A

4. Quick Check:

   Last cy.viewport() sets size = B [OK]

Hint: Last cy.viewport() call overrides previous sizes [OK]

Common Mistakes:

• Thinking first viewport call persists
• Assuming test fails on multiple viewport calls
• Confusing preset names with pixel sizes

4. You wrote this code but the viewport size does not change as expected:

cy.viewport(1024);

What is the problem?

medium

A. Viewport size must be set before visiting the page

B. cy.viewport() does not accept numbers

C. Missing height argument in cy.viewport()

D. cy.viewport() only accepts device names

Solution

1. Step 1: Check the cy.viewport() parameters

   The command requires both width and height as numbers, e.g., cy.viewport(1024, 768).

2. Step 2: Identify the error

   Only width (1024) is provided, height is missing, so viewport size won't change correctly.

3. Final Answer:

   Missing height argument in cy.viewport() -> Option C

4. Quick Check:

   Both width and height needed = A [OK]

Hint: Always provide width and height numbers in cy.viewport() [OK]

Common Mistakes:

• Passing only one number instead of two
• Thinking cy.viewport accepts only device names
• Believing viewport must be set before visiting page

5. You want to test your website's mobile and desktop views in one test. Which code snippet correctly sets the viewport to iPhone X size, runs a test, then changes to desktop size 1280x720 and runs another test?

hard

A. cy.viewport('iphone-x');\ncy.viewport(1280, 720);\ncy.get('#menu').should('be.visible');

B. cy.viewport('iphone-x', 1280, 720);\ncy.get('#menu').should('be.visible');

C. cy.viewport(1280, 720);\ncy.viewport('iphone-x');\ncy.get('#menu').should('be.visible');

D. cy.viewport('iphone-x');\ncy.get('#menu').should('be.visible');\ncy.viewport(1280, 720);\ncy.get('#menu').should('be.visible');

Solution

1. Step 1: Understand sequential viewport changes

   You can call cy.viewport() multiple times to change screen size during a test.

2. Step 2: Check the code snippets

   cy.viewport('iphone-x');\ncy.get('#menu').should('be.visible');\ncy.viewport(1280, 720);\ncy.get('#menu').should('be.visible'); sets iPhone X viewport, runs a check, then sets desktop viewport and runs the check again. This tests both views properly. cy.viewport('iphone-x', 1280, 720);\ncy.get('#menu').should('be.visible'); uses invalid syntax with multiple arguments. cy.viewport(1280, 720);\ncy.viewport('iphone-x');\ncy.get('#menu').should('be.visible'); changes viewport twice before any check. cy.viewport('iphone-x');\ncy.viewport(1280, 720);\ncy.get('#menu').should('be.visible'); runs only one check after both viewport changes, missing the first test.

3. Final Answer:

   Set viewport, test, change viewport, test again -> Option D

4. Quick Check:

   Change viewport before each test step = A [OK]

Hint: Call cy.viewport() before each test step to change screen size [OK]

Common Mistakes:

• Passing multiple sizes in one cy.viewport() call
• Changing viewport without running tests between
• Running tests only after last viewport change