Stubbing responses in Cypress - Framework Patterns

Framework Mode - Stubbing responses

Folder Structure

cypress/
├── e2e/                  # Test specs
│   └── example.cy.js     # Example test with stubbing
├── fixtures/             # Static test data files (JSON, etc.)
│   └── user.json         # Sample stub data
├── support/              # Custom commands and utilities
│   ├── commands.js       # Custom Cypress commands
│   └── index.js          # Support file loaded before tests
cypress.config.js         # Cypress configuration file

Test Framework Layers

• Test Specs (cypress/e2e): Contains test files where stubbing is used to simulate server responses.
• Fixtures (cypress/fixtures): Holds JSON or other files with stub data to return during tests.
• Support (cypress/support): Custom commands to simplify stubbing setup and reusable utilities.
• Configuration (cypress.config.js): Defines base URLs, environment variables, and test settings.

Configuration Patterns

• Environment Variables: Use env in cypress.config.js to set API base URLs or toggle stubbing on/off.
• Fixtures: Store stub response data in cypress/fixtures for easy reuse and maintenance.
• Custom Commands: Define commands like cy.stubResponse() in cypress/support/commands.js to centralize stubbing logic.
• Browser and Test Settings: Configure timeouts and retries in cypress.config.js to handle async stubbing behavior.

Test Reporting and CI/CD Integration

• Test Reports: Use Cypress built-in reporter or integrate with tools like Mochawesome for detailed HTML reports showing stubbed test results.
• CI/CD: Run Cypress tests with stubbing enabled in pipelines to ensure tests are fast and reliable without depending on real backend.
• Artifacts: Save screenshots and videos on test failures to help debug stub-related issues.

Best Practices

• Use Fixtures for Stub Data: Keep stub responses in separate files for clarity and easy updates.
• Centralize Stubbing Logic: Create reusable custom commands to avoid repeating stubbing code in tests.
• Stub Only What's Needed: Stub specific API calls relevant to the test to keep tests realistic.
• Keep Tests Independent: Avoid relying on real backend to make tests fast and stable.
• Document Stub Behavior: Comment why and how stubs are used to help team understanding.

Self Check

Where in this folder structure would you add a new stub response JSON file for a user profile API?

Key Result

Use fixtures and custom commands in Cypress to stub API responses for fast, reliable tests.

Practice

1. What is the main purpose of stubbing responses in Cypress testing?

easy

A. To fake server responses so tests run without a real backend

B. To speed up the browser rendering process

C. To automatically generate test data

D. To record user interactions for playback

Solution

1. Step 1: Understand stubbing concept

   Stubbing means faking server responses so the app can be tested without a real backend.

2. Step 2: Identify purpose in Cypress

   Cypress uses stubbing to isolate frontend tests from backend dependencies, making tests faster and more reliable.

3. Final Answer:

   To fake server responses so tests run without a real backend -> Option A

4. Quick Check:

   Stubbing = Fake server response [OK]

Hint: Stubbing fakes backend responses for isolated frontend tests [OK]

Common Mistakes:

• Thinking stubbing speeds up browser rendering
• Confusing stubbing with test data generation
• Believing stubbing records user actions

2. Which of the following is the correct syntax to stub a GET request to '/api/data' with Cypress?

easy

A. cy.stub('GET', '/api/data', { fixture: 'data.json' })

B. cy.route('GET', '/api/data', { fixture: 'data.json' })

C. cy.intercept('GET', '/api/data', { fixture: 'data.json' })

D. cy.mock('GET', '/api/data', { fixture: 'data.json' })

Solution

1. Step 1: Identify correct Cypress command

   The current Cypress command to stub network requests is cy.intercept().

2. Step 2: Check method and parameters

   Using cy.intercept('GET', '/api/data', { fixture: 'data.json' }) correctly stubs a GET request with a fixture response.

3. Final Answer:

   cy.intercept('GET', '/api/data', { fixture: 'data.json' }) -> Option C

4. Quick Check:

   Use cy.intercept for stubbing requests [OK]

Hint: Use cy.intercept for stubbing, not cy.stub or cy.route [OK]

Common Mistakes:

• Using cy.stub instead of cy.intercept
• Using deprecated cy.route command
• Using cy.mock which does not exist in Cypress

3. Given the code below, what will be the output of the test assertion?

cy.intercept('GET', '/users', { body: [{ id: 1, name: 'Alice' }] }).as('getUsers');
cy.visit('/users');
cy.wait('@getUsers').its('response.body[0].name').should('equal', 'Alice');

medium

A. Test passes because the stubbed response matches 'Alice'

B. Test fails because the alias '@getUsers' is not defined

C. Test fails because the response body is empty

D. Test throws a syntax error due to incorrect intercept usage

Solution

1. Step 1: Analyze the intercept stub

   The intercept stubs a GET request to '/users' with a response body containing one user named 'Alice'.

2. Step 2: Check the wait and assertion

   The test waits for '@getUsers' and asserts the first user's name equals 'Alice', which matches the stub.

3. Final Answer:

   Test passes because the stubbed response matches 'Alice' -> Option A

4. Quick Check:

   Stub response matches assertion = pass [OK]

Hint: Alias stub and assert matching response for pass [OK]

Common Mistakes:

• Assuming alias is undefined without .as()
• Thinking response body is empty
• Confusing syntax of cy.intercept

4. Identify the error in the following Cypress stub code:

cy.intercept('POST', '/login', { statusCode: 200, body: { token: 'abc123' } });
cy.visit('/login');
cy.wait('@loginRequest');

medium

A. cy.visit must come before cy.intercept

B. The HTTP method 'POST' is invalid in cy.intercept

C. The response body must be a string, not an object

D. The alias '@loginRequest' is missing because the intercept was not aliased

Solution

1. Step 1: Check alias usage

   The intercept is defined but not given an alias using .as(), so '@loginRequest' does not exist.

2. Step 2: Understand wait on alias

   Waiting on '@loginRequest' fails because the alias was never created.

3. Final Answer:

   The alias '@loginRequest' is missing because the intercept was not aliased -> Option D

4. Quick Check:

   Alias missing causes wait failure [OK]

Hint: Always alias intercept with .as() before waiting [OK]

Common Mistakes:

• Forgetting to add .as() to intercept
• Thinking POST is invalid method
• Believing response body must be string

5. You want to stub a GET request to '/products' that returns different responses based on a query parameter 'category'. Which is the best way to implement this in Cypress?

hard

A. Create multiple cy.intercept calls with the same URL but different responses

B. Use cy.intercept with a function handler to check req.query.category and send different responses

C. Use cy.intercept with a static response ignoring query parameters

D. Use cy.route with a fixture file for all categories

Solution

1. Step 1: Understand dynamic stubbing need

   Different responses based on query parameters require conditional logic in the stub.

2. Step 2: Use function handler in cy.intercept

   cy.intercept supports a function to inspect the request and send custom responses based on req.query.category.

3. Final Answer:

   Use cy.intercept with a function handler to check req.query.category and send different responses -> Option B

4. Quick Check:

   Function handler enables dynamic stubbing [OK]

Hint: Use function in cy.intercept for dynamic responses [OK]

Common Mistakes:

• Trying multiple intercepts with same URL (only last applies)
• Ignoring query parameters in stub
• Using deprecated cy.route instead of cy.intercept