Stubbing responses in Cypress - Test Execution Trace

Test Overview

This test stubs a network response for a user API call and verifies the UI shows the stubbed user name.

Test Code - Cypress

Cypress

describe('User API stub test', () => {
  it('stubs the /api/user response and checks UI', () => {
    cy.intercept('GET', '/api/user', { fixture: 'user.json' }).as('getUser');
    cy.visit('/profile');
    cy.wait('@getUser');
    cy.get('[data-cy=user-name]').should('contain.text', 'John Doe');
  });
});

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	cy.intercept stubs GET /api/user with fixture user.json and aliases it as getUser	No browser interaction yet, stub is ready	—	PASS
2	cy.visit navigates to /profile page	Browser loads /profile page, triggers GET /api/user request	—	PASS
3	cy.wait waits for the aliased getUser network call to complete	Stubbed response from user.json is returned instead of real API	Verify network call intercepted and stubbed response received	PASS
4	cy.get finds element with data-cy=user-name and checks its text	Page shows user name from stubbed response	Assert element text contains 'John Doe'	PASS

Failure Scenario

Failing Condition: The stub fixture file user.json is missing or malformed, or the selector [data-cy=user-name] does not exist on the page

Execution Trace Quiz - 3 Questions

What does cy.intercept do in this test?

A It replaces the real API response with a stubbed fixture

B It navigates to the profile page

C It waits for the network call to finish

D It checks the text of an element

Key Result

Stubbing network responses isolates tests from backend changes and makes UI tests faster and more reliable.

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