Component test setup in Cypress - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Cypress component test setup code?

Consider this Cypress test setup for a React component. What will be the test result after running this code?

Cypress

import { mount } from 'cypress/react';

describe('Button component', () => {
  it('renders with correct label', () => {
    mount(<button>Click me</button>);
    cy.get('button').should('have.text', 'Click me');
  });
});

A Test fails because the button text is empty.

B Test passes because the button text matches 'Click me'.

C Test fails due to a syntax error in the mount function.

D Test fails because the selector 'button' does not find any element.

💡 Hint

Think about what the mount function does and how Cypress queries elements.

The mount function renders the React component inside the Cypress test runner. The cy.get('button') finds the button element, and the assertion checks its text. Since the button text is 'Click me', the test passes.

❓ locator

intermediate

Which locator is best for selecting a button in a Cypress component test?

You want to select a button in a component test for Cypress. Which locator is the best practice to use?

A cy.get('button')

B cy.get('#submit')

C cy.get('.btn-primary')

D cy.get('[data-cy="submit-button"]')

💡 Hint

Consider maintainability and avoiding brittle selectors.

Using data-cy attributes is a best practice for Cypress tests because it avoids relying on styling classes or IDs that may change. This makes tests more stable and easier to maintain.

❓ assertion

advanced

Which assertion correctly verifies a component's input value in Cypress?

You have an input field rendered in a component test. Which assertion correctly checks that the input's value is 'hello'?

Cypress

import { mount } from 'cypress/react';

mount(<input value="hello" />);

A cy.get('input').should('have.value', 'hello')

B cy.get('input').should('contain.text', 'hello')

C cy.get('input').should('have.attr', 'value', 'hello')

D cy.get('input').should('have.text', 'hello')

💡 Hint

Think about how input values are accessed in Cypress assertions.

The have.value assertion checks the value property of input elements. Using contain.text or have.text does not work for input values because inputs do not have inner text. Checking the attribute value may not reflect the current value if changed dynamically.

🔧 Debug

advanced

Why does this Cypress component test fail to find the button?

Look at this test code. Why does the test fail with 'Timed out retrying: Expected to find element: button, but never found it'?

Cypress

import { mount } from 'cypress/react';

describe('MyComponent', () => {
  it('should find the button', () => {
    cy.get('button').should('exist');
    mount(<button>Press</button>);
  });
});

A The test is missing a wait command before cy.get.

B The selector 'button' is incorrect and does not match the button element.

C The mount call happens after the cy.get, so the button is not rendered when searched.

D The mount function is not imported, causing the test to fail.

💡 Hint

Think about the order of commands and when elements appear in the DOM.

Cypress commands run asynchronously in order. The cy.get('button') runs before the component is mounted, so no button exists yet. The test fails because it looks for the button too early.

❓ framework

expert

Which Cypress configuration is required to enable component testing with React?

You want to run Cypress component tests for React components. Which configuration setting is necessary in cypress.config.js?

A component: { devServer: { framework: 'react', bundler: 'webpack' } }

B component: { supportFile: false }

C e2e: { baseUrl: 'http://localhost:3000' }

D component: { testFiles: '**/*.spec.js' }

💡 Hint

Think about how Cypress knows which framework and bundler to use for component tests.

To run component tests with React, Cypress needs to know the framework and bundler to use. The component.devServer config with framework: 'react' and bundler: 'webpack' tells Cypress how to build and serve the components for testing.

Practice

1. What is the main purpose of using mount() in Cypress component testing?

easy

A. To write unit tests for backend APIs

B. To run end-to-end tests on the whole application

C. To load a component inside Cypress for testing

D. To deploy the application to a server

Solution

1. Step 1: Understand the role of mount()

   mount() is used to load a UI component inside Cypress so you can test it in isolation.

2. Step 2: Differentiate from other test types

   End-to-end tests run the whole app, but mount() focuses on small parts (components).

3. Final Answer:

   To load a component inside Cypress for testing -> Option C

4. Quick Check:

   mount() loads component [OK]

Hint: Remember: mount() loads components, not full apps [OK]

Common Mistakes:

• Confusing mount() with full app testing
• Thinking mount() deploys code
• Mixing component and API testing

2. Which of the following is the correct syntax to prepare a component before each test in Cypress?

easy

A. beforeEach(() => { mount() })

B. beforeAll(() => { mount() })

C. afterEach(() => { mount() })

D. before(() => { mount() })

Solution

1. Step 1: Identify the correct hook for setup before each test

   beforeEach() runs before every test, ideal for fresh component setup.

2. Step 2: Confirm syntax correctness

   The syntax beforeEach(() => { mount(<MyComponent />) }) correctly mounts the component before each test.

3. Final Answer:

   beforeEach(() => { mount(<MyComponent />) }) -> Option A

4. Quick Check:

   Use beforeEach() for setup [OK]

Hint: Use beforeEach() to reset component before every test [OK]

Common Mistakes:

• Using beforeAll() which runs only once
• Using afterEach() which runs after tests
• Using before() which is deprecated in Cypress

3. Given this Cypress component test code, what will be the output in the test runner?

describe('Button component', () => {
  beforeEach(() => {
    mount(Click me)
  })

  it('checks button text', () => {
    cy.get('button').should('have.text', 'Click me')
  })
})

medium

A. Test passes because button text matches

B. Test fails because button text is missing

C. Test errors due to wrong selector syntax

D. Test is skipped because mount() is missing

Solution

1. Step 1: Analyze the mount and selector

   The mount() loads a button with text 'Click me'. The selector cy.get('button') correctly targets it.

2. Step 2: Check the assertion

   The assertion should('have.text', 'Click me') matches the button's text exactly, so it passes.

3. Final Answer:

   Test passes because button text matches -> Option A

4. Quick Check:

   Correct selector and text = pass [OK]

Hint: Match selector text exactly for passing assertion [OK]

Common Mistakes:

• Using wrong selector causing no element found
• Mismatching text in assertion
• Forgetting to mount component before test

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

describe('Input component', () => {
  beforeEach(() => {
    mount('')
  })

  it('checks placeholder', () => {
    cy.get('input').should('have.attr', 'placeholder', 'Enter name')
  })
})

medium

A. beforeEach() should be replaced with afterEach()

B. mount() should receive JSX, not a string

C. cy.get() selector is incorrect

D. The placeholder attribute is misspelled

Solution

1. Step 1: Check the argument passed to mount()

   The code passes a string '<input placeholder="Enter name" />' instead of JSX element. mount() expects JSX, not a string.

2. Step 2: Confirm other parts are correct

   The selector cy.get('input') and attribute check are correct, so no error there.

3. Final Answer:

   mount() should receive JSX, not a string -> Option B

4. Quick Check:

   mount() needs JSX, not string [OK]

Hint: Pass JSX, not strings, to mount() [OK]

Common Mistakes:

• Passing HTML strings instead of JSX to mount()
• Confusing beforeEach() with afterEach()
• Using wrong selectors

5. You want to test a component that renders a list of items passed as props. Which setup correctly mounts the component with props before each test?

hard

A. beforeEach(() => { mount() })

B. beforeEach(() => { mount('') })

C. beforeEach(() => { mount(List, { props: { items: ["a", "b"] } }) })

D. beforeEach(() => { mount() })

Solution

1. Step 1: Understand correct JSX with props

   Passing props in JSX uses syntax like <List items={["a", "b"]} />. This is correct in beforeEach(() => { mount(<List items={["a", "b"]} />) }).

2. Step 2: Identify incorrect options

   beforeEach(() => { mount('<List items=["a", "b"] />') }) passes a string, not JSX. beforeEach(() => { mount(List, { props: { items: ["a", "b"] } }) }) uses wrong mount signature. beforeEach(() => { mount(<List items="a,b" />) }) passes a string instead of array.

3. Final Answer:

   beforeEach(() => { mount(<List items={["a", "b"]} />) }) -> Option D

4. Quick Check:

   Use JSX with array props [OK]

Hint: Pass props as JSX arrays, not strings [OK]

Common Mistakes:

• Passing component as string instead of JSX
• Using wrong mount function signature
• Passing props as comma-separated string