Preserving state between tests in Cypress

Introduction

Sometimes tests need to remember things like login info so you don't have to do the same steps again and again.

You want to stay logged in across multiple tests without logging in each time.

You need to keep cookies or local storage data between tests.

You want faster tests by skipping repeated setup steps.

You want to test a flow that spans multiple pages or actions.

You want to avoid flaky tests caused by resetting state too often.

Syntax

Cypress

Cypress.Cookies.preserveOnce('cookieName1', 'cookieName2')

// or

Cypress.Cookies.defaults({ preserve: ['cookieName'] })

Use preserveOnce inside a beforeEach hook to keep cookies for that test run only.

Use defaults to keep cookies for all tests automatically.

Examples

This keeps the 'session_id' and 'auth_token' cookies between tests so you stay logged in.

Cypress

beforeEach(() => {
  Cypress.Cookies.preserveOnce('session_id', 'auth_token')
})

This tells Cypress to always keep the 'session_id' cookie for all tests in the file.

Cypress

Cypress.Cookies.defaults({
  preserve: ['session_id']
})

Log in once before all tests, then keep the session cookie for each test.

Cypress

before(() => {
  cy.login() // custom command to log in once
})

beforeEach(() => {
  Cypress.Cookies.preserveOnce('session_id')
})

Sample Program

This test suite logs in once before all tests. Then it keeps the 'session_id' cookie between tests so the user stays logged in. Test 1 checks the dashboard greeting. Test 2 visits the profile page without logging in again.

Cypress

describe('Preserve login state between tests', () => {
  before(() => {
    cy.visit('/login')
    cy.get('#username').type('user1')
    cy.get('#password').type('password123')
    cy.get('button[type=submit]').click()
    cy.url().should('include', '/dashboard')
  })

  beforeEach(() => {
    Cypress.Cookies.preserveOnce('session_id')
  })

  it('Test 1: Check dashboard greeting', () => {
    cy.visit('/dashboard')
    cy.contains('Welcome, user1').should('be.visible')
  })

  it('Test 2: Visit profile page without logging in again', () => {
    cy.visit('/profile')
    cy.contains('user1').should('be.visible')
  })
})

Important Notes

Preserving cookies is the most common way to keep login state.

You can also preserve local storage or session storage using custom commands.

Be careful: preserving too much state can make tests depend on each other, which is not ideal.

Summary

Preserving state helps tests run faster and avoid repeating steps.

Use Cypress.Cookies.preserveOnce or Cypress.Cookies.defaults to keep cookies.

Keep tests independent by preserving only what is necessary.

Practice

1. What is the main reason to preserve state between tests in Cypress?

easy

A. To clear all cookies after each test

B. To make tests dependent on each other

C. To avoid repeating login steps and speed up test execution

D. To disable assertions in tests

Solution

1. Step 1: Understand test state preservation

   Preserving state means keeping some data like cookies so tests don't repeat setup steps.

2. Step 2: Identify the benefit

   Keeping state avoids repeating login or setup, making tests faster and more efficient.

3. Final Answer:

   To avoid repeating login steps and speed up test execution -> Option C

4. Quick Check:

   Preserving state = faster tests [OK]

Hint: Preserve state to skip repeated steps and save time [OK]

Common Mistakes:

• Thinking tests should be dependent on each other
• Believing preserving state clears cookies
• Assuming preserving state disables assertions

2. Which of the following is the correct syntax to preserve a cookie named 'session_id' only once in Cypress?

easy

A. Cypress.Cookies.preserveOnce('session_id')

B. cy.preserveCookie('session_id')

C. Cypress.preserveCookieOnce('session_id')

D. cy.Cookies.preserve('session_id')

Solution

1. Step 1: Recall Cypress cookie preservation method

   The correct method to preserve cookies once is Cypress.Cookies.preserveOnce.

2. Step 2: Match method and argument

   The method takes the cookie name as a string argument, e.g., 'session_id'.

3. Final Answer:

   Cypress.Cookies.preserveOnce('session_id') -> Option A

4. Quick Check:

   Preserve once = Cypress.Cookies.preserveOnce [OK]

Hint: Use Cypress.Cookies.preserveOnce('cookieName') to keep cookies once [OK]

Common Mistakes:

• Using cy.preserveCookie which does not exist
• Mixing method names like preserveCookieOnce
• Calling preserve on cy.Cookies which is invalid

3. Given the following Cypress test code, what will be the output of the second test?

describe('Test Suite', () => {
  beforeEach(() => {
    Cypress.Cookies.preserveOnce('token')
  })

  it('Test 1: Set cookie', () => {
    cy.setCookie('token', 'abc123')
  })

  it('Test 2: Check cookie', () => {
    cy.getCookie('token').should('have.property', 'value', 'abc123')
  })
})

medium

A. Test 2 passes because the 'token' cookie is preserved

B. Test 2 fails because cookies are cleared between tests

C. Test 2 throws a syntax error

D. Test 2 passes but the cookie value is empty

Solution

1. Step 1: Analyze cookie preservation in beforeEach

   The beforeEach hook preserves the 'token' cookie between tests using Cypress.Cookies.preserveOnce('token').

2. Step 2: Understand cookie setting and checking

   Test 1 sets the cookie 'token' to 'abc123'. Test 2 checks the cookie value. Since the cookie is preserved, the check passes.

3. Final Answer:

   Test 2 fails because cookies are cleared between tests -> Option B

4. Quick Check:

   PreserveOnce keeps cookie for next test [OK]

Hint: Preserve cookie in beforeEach to keep it for next test [OK]

Common Mistakes:

• Assuming cookies clear automatically between tests
• Thinking preserveOnce clears cookies
• Confusing syntax causing errors

4. You wrote this code to preserve cookies but the second test fails because the cookie is missing:

beforeEach(() => {
  Cypress.Cookies.preserveOnce('auth_token')
})

it('Login test', () => {
  cy.setCookie('auth_token', 'xyz789')
})

it('Dashboard test', () => {
  cy.getCookie('auth_token').should('exist')
})

What is the likely cause of the failure?

medium

A. The cookie is set after the beforeEach hook runs, so it is not preserved

B. The cookie name is misspelled in preserveOnce

C. Cypress cannot preserve cookies between tests

D. The assertion syntax is incorrect

Solution

1. Step 1: Understand when preserveOnce runs

   The beforeEach hook runs before each test, so it preserves cookies existing before the test starts.

2. Step 2: Analyze cookie setting timing

   The cookie is set inside the first test, after beforeEach runs, so it is not preserved for the next test.

3. Final Answer:

   The cookie is set after the beforeEach hook runs, so it is not preserved -> Option A

4. Quick Check:

   PreserveOnce must run after cookie set [OK]

Hint: Set cookies before preserveOnce runs to keep them [OK]

Common Mistakes:

• Thinking preserveOnce preserves cookies set during the test
• Assuming Cypress can't preserve cookies
• Blaming assertion syntax instead of timing

5. You want to preserve multiple cookies named 'token' and 'user_id' across all tests without calling preserveOnce in every test. Which is the best way to do this in Cypress?

hard

A. Disable cookie clearing globally with Cypress.config

B. Call Cypress.Cookies.preserveOnce('token', 'user_id') in each test

C. Set cookies again in every test manually

D. Use Cypress.Cookies.defaults({ whitelist: ['token', 'user_id'] }) in support file

Solution

1. Step 1: Understand preserving multiple cookies globally

   Using Cypress.Cookies.defaults with a preserve array keeps specified cookies across all tests automatically.

2. Step 2: Compare with other options

   Calling preserveOnce in every test is repetitive. Manually setting cookies each time is inefficient. Disabling cookie clearing globally is not recommended.

3. Final Answer:

   Use Cypress.Cookies.defaults({ whitelist: ['token', 'user_id'] }) in support file -> Option D

4. Quick Check:

   Defaults preserve multiple cookies globally [OK]

Hint: Use Cypress.Cookies.defaults to preserve cookies globally [OK]

Common Mistakes:

• Calling preserveOnce repeatedly instead of defaults
• Manually resetting cookies each test
• Trying to disable cookie clearing globally