Component testing vs E2E in Cypress - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a Cypress component test for a Button component.

Cypress

describe('Button component', () => {
  it('renders correctly', () => {
    cy.[1](<Button />)
  })
})

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

Aget

Bvisit

Cmount

Dclick

Attempts:

3 left

💡 Hint

Common Mistakes

Using cy.visit() which is for page navigation, not component rendering.

In Cypress component testing, cy.mount() is used to render the component for testing.

2fill in blank

medium

Complete the code to start an E2E test visiting the home page.

Cypress

describe('Home page', () => {
  it('loads successfully', () => {
    cy.[1]('/')
  })
})

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

Avisit

Bmount

Cclick

Dcontains

Attempts:

3 left

💡 Hint

Common Mistakes

Using cy.mount() which is for component tests, not E2E page visits.

In Cypress E2E tests, cy.visit() is used to open a web page URL.

3fill in blank

hard

Fix the error in the E2E test code to check if a button with text 'Submit' exists.

Cypress

cy.get('button').[1]('Submit')

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

Avisit

Bcontains

Cmount

Dclick

Attempts:

3 left

💡 Hint

Common Mistakes

Using cy.get('button').click('Submit') which is invalid syntax.

The contains command finds an element with specific text content.

4fill in blank

hard

Fill both blanks to create a component test that mounts a component and checks if it contains text 'Hello'.

Cypress

cy.[1](<Greeting />)
cy.get('div').[2]('Hello')

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

Amount

Bclick

Ccontains

Dvisit

Attempts:

3 left

💡 Hint

Common Mistakes

Using cy.visit() in component tests or cy.get().click() instead of contains.

First, mount renders the component. Then, contains checks for text inside an element.

5fill in blank

hard

Fill all three blanks to write an E2E test that visits the login page, types username, and clicks the submit button.

Cypress

cy.[1]('/login')
cy.get('input[name="username"]').[2]('user123')
cy.get('button[type="submit"]').[3]()

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

Amount

Btype

Cclick

Dvisit

Attempts:

3 left

💡 Hint

Common Mistakes

Using mount in E2E tests or missing the click action on the button.

Use visit to open the page, type to enter text, and click to press the button.

Practice

1. What is the main focus of component testing in Cypress?

easy

A. Testing the entire app flow from start to finish

B. Testing individual parts of the app in isolation

C. Checking the app's performance under load

D. Verifying database connections

Solution

1. Step 1: Understand component testing scope

   Component testing focuses on small parts or components of the app, testing them alone without the full app context.

2. Step 2: Compare with other testing types

   E2E testing checks the whole app working together, so it is not the focus of component testing.

3. Final Answer:

   Testing individual parts of the app in isolation -> Option B

4. Quick Check:

   Component testing = isolated parts [OK]

Hint: Component testing isolates parts, not full app [OK]

Common Mistakes:

• Confusing component testing with E2E testing
• Thinking component testing checks full app flow
• Assuming component testing checks performance

2. Which of the following is the correct Cypress command to mount a React component for component testing?

easy

A. cy.visit('/component')

B. cy.request('/api/component')

C. cy.mount()

D. cy.get('MyComponent').click()

Solution

1. Step 1: Identify component testing command

   In Cypress component testing, cy.mount() is used to render a component in isolation.

2. Step 2: Eliminate other commands

   cy.visit() is for E2E page visits, cy.get() selects elements, and cy.request() makes HTTP calls, none mount components.

3. Final Answer:

   cy.mount(<MyComponent />) -> Option C

4. Quick Check:

   Mount component = cy.mount() [OK]

Hint: Use cy.mount() to render components in tests [OK]

Common Mistakes:

• Using cy.visit() for component testing
• Confusing cy.get() with mounting
• Trying to mount components with cy.request()

3. Given this Cypress E2E test code, what will be the output in the test report?

describe('Login flow', () => {
  it('should show error on wrong password', () => {
    cy.visit('/login')
    cy.get('input[name="username"]').type('user1')
    cy.get('input[name="password"]').type('wrongpass')
    cy.get('button[type="submit"]').click()
    cy.contains('Invalid credentials').should('be.visible')
  })
})

medium

A. Test passes without checking any message

B. Test fails because cy.visit() is not allowed in E2E

C. Test fails due to syntax error in selectors

D. Test passes if 'Invalid credentials' message appears

Solution

1. Step 1: Analyze test steps

   The test visits the login page, enters username and wrong password, clicks submit, then checks for error message visibility.

2. Step 2: Verify correctness of commands

   All commands are valid Cypress E2E commands. The assertion checks if the error message is visible, so test passes if message appears.

3. Final Answer:

   Test passes if 'Invalid credentials' message appears -> Option D

4. Quick Check:

   E2E test passes if error message visible [OK]

Hint: E2E tests check full flow and visible messages [OK]

Common Mistakes:

• Thinking cy.visit() is invalid in E2E
• Ignoring the assertion on error message
• Assuming syntax errors in selectors without cause

4. Identify the error in this Cypress component test code:

import MyButton from './MyButton'
describe('MyButton component', () => {
  it('renders button text', () => {
    cy.mount(MyButton)
    cy.get('button').should('contain.text', 'Click me')
  })
})

medium

A. Missing JSX syntax when mounting component

B. cy.get selector is incorrect

C. cy.mount cannot be used in component tests

D. No assertion is present

Solution

1. Step 1: Check component mounting syntax

   In Cypress component testing, components must be mounted using JSX syntax like cy.mount(<MyButton />), not just the component name.

2. Step 2: Verify other parts

   The selector cy.get('button') and assertion are correct. cy.mount is valid in component tests.

3. Final Answer:

   Missing JSX syntax when mounting component -> Option A

4. Quick Check:

   Use JSX syntax in cy.mount() [OK]

Hint: Always wrap component in <> when mounting [OK]

Common Mistakes:

• Passing component without JSX syntax to cy.mount
• Thinking cy.mount is invalid in component tests
• Misreading selector as incorrect

5. You want to test a login form component in isolation but also verify the full login flow including navigation. Which Cypress testing approach should you use for each task?

hard

A. Use component testing for form UI; use E2E testing for full login flow

B. Use E2E testing for form UI; use component testing for full login flow

C. Use only component testing for both tasks

D. Use only E2E testing for both tasks

Solution

1. Step 1: Match testing types to tasks

   Component testing is best for isolated UI parts like the login form component itself.

2. Step 2: Use E2E for full app flow

   To verify the entire login flow including navigation and backend, E2E testing is appropriate.

3. Final Answer:

   Use component testing for form UI; use E2E testing for full login flow -> Option A

4. Quick Check:

   Component = UI parts, E2E = full flow [OK]

Hint: Component tests parts; E2E tests whole app flow [OK]

Common Mistakes:

• Mixing up which test type suits UI vs full flow
• Trying to test full flow with component tests
• Ignoring navigation in login flow testing