Test isolation strategies in Cypress - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is test isolation in software testing?

Test isolation means running each test independently so that tests do not affect each other. This helps find bugs more easily and keeps tests reliable.

beginner

Why should tests be isolated when using Cypress?

Isolated tests prevent shared state or data from causing false results. Cypress runs tests in the same browser session, so isolation avoids interference between tests.

intermediate

Name two common strategies to isolate tests in Cypress.

1. Reset application state before each test (e.g., clear database or local storage). 2. Use Cypress commands like cy.visit() to reload the page fresh for each test.

beginner

How does using cy.visit() help with test isolation?

cy.visit() reloads the web page, clearing any temporary data or UI changes from previous tests. This ensures each test starts with a clean page.

beginner

What is a downside of poor test isolation?

Tests can pass or fail unpredictably because they depend on leftover data or state from other tests. This makes debugging harder and reduces trust in test results.

What does test isolation ensure in Cypress tests?

A Each test runs independently without affecting others

B Tests share the same browser session data

C Tests run faster by skipping page reloads

D Tests depend on previous test results

Test isolation means each test runs independently so they don't affect each other.

Which Cypress command helps reset the page state between tests?

A cy.reload()

B cy.clearCookies()

C cy.visit()

D cy.get()

cy.visit() loads a fresh page, helping isolate tests by resetting the UI state.

Why is clearing local storage important for test isolation?

A It speeds up tests

B It prevents leftover data from affecting other tests

C It changes the test order

D It disables browser caching

Clearing local storage removes leftover data that could cause tests to interfere with each other.

What can happen if tests are not isolated?

A Tests may fail unpredictably due to shared state

B Tests always pass

C Tests run in parallel

D Tests run faster

Without isolation, tests can fail unpredictably because they depend on leftover data or state.

Which is NOT a good practice for test isolation in Cypress?

A Clearing cookies and local storage

B Using cy.visit() to reload pages

C Resetting database state before tests

D Sharing user login state across tests

Sharing login state across tests can cause tests to depend on each other, breaking isolation.

Explain why test isolation is important in Cypress and describe two ways to achieve it.

Think about how leftover data or UI changes can affect other tests.

Describe the risks of not isolating tests and how it affects test reliability.

Consider what happens if one test changes something another test depends on.

Practice

1. What is the main purpose of test isolation in Cypress testing?

easy

A. To speed up test execution by running all tests together

B. To share data between tests for faster setup

C. To keep tests independent and avoid interference between them

D. To reduce the number of tests needed

Solution

1. Step 1: Understand test isolation concept

   Test isolation means each test runs independently without relying on others.

2. Step 2: Identify the main benefit

   This independence avoids interference and makes tests reliable and easier to debug.

3. Final Answer:

   To keep tests independent and avoid interference between them -> Option C

4. Quick Check:

   Test isolation = Independent tests [OK]

Hint: Test isolation means no test depends on another [OK]

Common Mistakes:

• Thinking tests should share data to run faster
• Believing test isolation reduces total tests
• Confusing isolation with parallel execution

2. Which Cypress hook is best used to reset application state before each test to ensure isolation?

easy

A. beforeEach

B. before

C. after

D. afterEach

Solution

1. Step 1: Recall Cypress hooks purpose

   beforeEach runs before every test, ideal for resetting state.

2. Step 2: Compare with other hooks

   before runs once before all tests, after and afterEach run after tests, so they don't reset state before tests.

3. Final Answer:

   beforeEach -> Option A

4. Quick Check:

   Reset state before each test = beforeEach [OK]

Hint: Use beforeEach to reset state before every test [OK]

Common Mistakes:

• Using before which runs only once
• Confusing afterEach with beforeEach
• Not resetting state at all

3. Consider this Cypress test code snippet:

describe('My Tests', () => {
  beforeEach(() => {
    cy.visit('/login')
  })

  it('Test A', () => {
    cy.get('#username').type('user1')
    cy.get('#password').type('pass1')
    cy.get('button').click()
    cy.url().should('include', '/dashboard')
  })

  it('Test B', () => {
    cy.get('#username').type('user2')
    cy.get('#password').type('pass2')
    cy.get('button').click()
    cy.url().should('include', '/dashboard')
  })
})

What is the main benefit of using beforeEach here?

medium

A. It visits the login page once before all tests

B. It visits the login page before each test to isolate them

C. It skips the login page for Test B

D. It runs tests faster by sharing the login page

Solution

1. Step 1: Analyze beforeEach usage

   beforeEach runs before every test, so it visits the login page before Test A and Test B.

2. Step 2: Understand test isolation effect

   This ensures each test starts fresh on the login page, isolating tests and avoiding state carryover.

3. Final Answer:

   It visits the login page before each test to isolate them -> Option B

4. Quick Check:

   beforeEach = fresh start per test [OK]

Hint: beforeEach runs before every test, isolating them [OK]

Common Mistakes:

• Thinking beforeEach runs only once
• Assuming tests share the same page state
• Believing it skips steps for some tests

4. You wrote tests with beforeEach to reset state, but tests still fail due to shared data. What is the likely mistake?

medium

A. Using before instead of beforeEach

B. Not visiting the page in any hook

C. Using afterEach to reset state

D. Running tests in parallel

Solution

1. Step 1: Identify hook usage problem

   If before is used, it runs once before all tests, so state is not reset before each test.

2. Step 2: Understand impact on test isolation

   This causes shared data between tests, breaking isolation and causing failures.

3. Final Answer:

   Using before instead of beforeEach -> Option A

4. Quick Check:

   beforeEach resets state per test, before does not [OK]

Hint: Use beforeEach, not before, to reset state each test [OK]

Common Mistakes:

• Confusing before and beforeEach hooks
• Assuming afterEach resets state before tests
• Ignoring test parallelism effects

5. You want to run Cypress tests in parallel on CI to speed up testing. Which test isolation strategy helps ensure tests run reliably in parallel?

hard

A. Sharing global variables between tests

B. Running all tests in a single browser session without reset

C. Disabling test retries to avoid repeated runs

D. Using beforeEach to reset state and avoid shared data

Solution

1. Step 1: Understand parallel test challenges

   Parallel tests run simultaneously, so shared state causes flaky failures.

2. Step 2: Identify isolation strategy for parallel runs

   Using beforeEach to reset state and avoid shared data ensures each test is independent and reliable.

3. Final Answer:

   Using beforeEach to reset state and avoid shared data -> Option D

4. Quick Check:

   Parallel tests need isolated state = beforeEach [OK]

Hint: Reset state before each test for reliable parallel runs [OK]

Common Mistakes:

• Sharing global variables causing conflicts
• Running tests without resetting state
• Disabling retries instead of fixing isolation