Local storage management in Cypress

Introduction

Local storage lets websites save small bits of data on your browser. Managing it in tests helps check if data is saved or cleared correctly.

When you want to test if a website saves user preferences locally.

When you need to clear saved data before starting a new test.

When you want to check if data is correctly removed after logout.

When testing if local storage updates after certain actions.

When verifying that local storage data persists after page reload.

Syntax

Cypress

cy.window().then(win => {
  // Get local storage item
  const item = win.localStorage.getItem('key')

  // Set local storage item
  win.localStorage.setItem('key', 'value')

  // Remove local storage item
  win.localStorage.removeItem('key')

  // Clear all local storage
  win.localStorage.clear()
})

Use cy.window() to access the browser's window object where local storage lives.

Always perform local storage actions inside then() to ensure Cypress waits for the window object.

Examples

This saves the value 'dark' under the key 'theme' in local storage.

Cypress

cy.window().then(win => {
  win.localStorage.setItem('theme', 'dark')
})

This reads the 'theme' value and checks if it equals 'dark'.

Cypress

cy.window().then(win => {
  const theme = win.localStorage.getItem('theme')
  expect(theme).to.equal('dark')
})

This removes the 'theme' item from local storage.

Cypress

cy.window().then(win => {
  win.localStorage.removeItem('theme')
})

This clears all items from local storage.

Cypress

cy.window().then(win => {
  win.localStorage.clear()
})

Sample Program

This test visits a page, saves a local storage item, checks it, removes it, and confirms it is gone.

Cypress

describe('Local Storage Management Test', () => {
  it('should save, read, and clear local storage', () => {
    cy.visit('https://example.cypress.io')

    // Save item
    cy.window().then(win => {
      win.localStorage.setItem('user', 'Alice')
    })

    // Check saved item
    cy.window().then(win => {
      const user = win.localStorage.getItem('user')
      expect(user).to.equal('Alice')
    })

    // Remove item
    cy.window().then(win => {
      win.localStorage.removeItem('user')
    })

    // Confirm removal
    cy.window().then(win => {
      const user = win.localStorage.getItem('user')
      expect(user).to.be.null
    })
  })
})

Important Notes

Local storage is shared per domain, so tests on different sites have separate storage.

Use cy.clearLocalStorage() as a shortcut to clear storage if preferred.

Remember local storage stores only strings, so convert objects with JSON.stringify() and JSON.parse().

Summary

Local storage holds small data in the browser for a website.

Cypress uses cy.window() to access and manage local storage.

Tests can save, read, remove, and clear local storage to check app behavior.

Practice

1. What is the primary purpose of local storage in a web browser when testing with Cypress?

easy

A. To run JavaScript code on the server

B. To store small amounts of data persistently for a website

C. To style the webpage dynamically

D. To manage network requests

Solution

1. Step 1: Understand local storage role

   Local storage is used by browsers to save small data like user preferences or tokens persistently.

2. Step 2: Connect with Cypress testing

   Cypress can access this storage to verify or manipulate data during tests.

3. Final Answer:

   To store small amounts of data persistently for a website -> Option B

4. Quick Check:

   Local storage = persistent small data [OK]

Hint: Local storage saves small data for the site, not server tasks [OK]

Common Mistakes:

• Confusing local storage with server-side storage
• Thinking local storage runs code
• Mixing local storage with styling or network

2. Which Cypress command is used to access the browser's window object to manage local storage?

easy

A. cy.document()

B. cy.getLocalStorage()

C. cy.localStorage()

D. cy.window()

Solution

1. Step 1: Recall Cypress commands for browser objects

   To access the browser's window object, Cypress provides cy.window().

2. Step 2: Understand local storage access

   Local storage is a property of the window object, so cy.window() is used to reach it.

3. Final Answer:

   cy.window() -> Option D

4. Quick Check:

   Access window with cy.window() [OK]

Hint: Use cy.window() to reach local storage via window object [OK]

Common Mistakes:

• Using non-existent commands like cy.getLocalStorage()
• Confusing cy.document() with window object
• Assuming cy.localStorage() exists

3. What will be the output of the following Cypress code snippet?

cy.window().then(win => {
  win.localStorage.setItem('user', 'Alice');
  const user = win.localStorage.getItem('user');
  cy.wrap(user).should('equal', 'Alice');
});

medium

A. Test will fail due to syntax error in setItem usage

B. Test will fail because localStorage is not accessible

C. Test will pass because 'user' is set and retrieved correctly

D. Test will pass but 'user' will be undefined

Solution

1. Step 1: Analyze localStorage set and get

   The code sets 'user' key to 'Alice' in localStorage, then retrieves it correctly.

2. Step 2: Check assertion correctness

   The assertion checks if retrieved value equals 'Alice', which is true, so test passes.

3. Final Answer:

   Test will pass because 'user' is set and retrieved correctly -> Option C

4. Quick Check:

   Set and get localStorage works, test passes [OK]

Hint: Setting then getting localStorage key returns correct value [OK]

Common Mistakes:

• Assuming localStorage is inaccessible in Cypress
• Thinking setItem syntax is wrong
• Expecting undefined instead of stored value

4. Identify the error in this Cypress code that tries to clear local storage:

cy.window().then(win => {
  win.localStorage.clear;
});

medium

A. Missing parentheses to call clear method

B. localStorage.clear requires a key argument

C. cy.window() cannot access localStorage

D. clear is not a function of localStorage

Solution

1. Step 1: Check localStorage clear usage

   localStorage.clear is a function and must be called with parentheses: clear()

2. Step 2: Identify missing parentheses error

   The code uses clear without parentheses, so it does not execute the function.

3. Final Answer:

   Missing parentheses to call clear method -> Option A

4. Quick Check:

   Call clear() with parentheses to clear storage [OK]

Hint: Always add () to call localStorage.clear() method [OK]

Common Mistakes:

• Forgetting parentheses when calling functions
• Thinking clear needs a key argument
• Assuming cy.window() can't access localStorage

5. You want to write a Cypress test that saves a token in local storage, reloads the page, and then verifies the token is still present. Which sequence of commands correctly achieves this?

hard

A. cy.window().then(win => win.localStorage.setItem('token', 'abc123')); cy.reload(); cy.window().then(win => expect(win.localStorage.getItem('token')).to.equal('abc123'));

B. cy.setLocalStorage('token', 'abc123'); cy.reload(); cy.getLocalStorage('token').should('equal', 'abc123');

C. cy.window().then(win => win.localStorage.setItem('token', 'abc123')); cy.reload(); cy.window().its('localStorage.token').should('equal', 'abc123');

D. cy.window().then(win => win.localStorage.clear()); cy.reload(); cy.window().its('localStorage.token').should('be.null');

Solution

1. Step 1: Save token in localStorage correctly

   Using cy.window().then(win => win.localStorage.setItem('token', 'abc123')) correctly sets the token.

2. Step 2: Reload and verify token presence

   After cy.reload(), accessing localStorage via cy.window().then and asserting with expect ensures token is still 'abc123'.

3. Step 3: Evaluate other options

   cy.window().then(win => win.localStorage.setItem('token', 'abc123')); cy.reload(); cy.window().its('localStorage.token').should('equal', 'abc123'); uses incorrect property access for localStorage token; cy.setLocalStorage('token', 'abc123'); cy.reload(); cy.getLocalStorage('token').should('equal', 'abc123'); uses non-existent commands; cy.window().then(win => win.localStorage.clear()); cy.reload(); cy.window().its('localStorage.token').should('be.null'); clears storage and checks for null, which is not the goal.

4. Final Answer:

   Use cy.window() to set, reload, then check with expect -> Option A

5. Quick Check:

   Set, reload, then assert with cy.window() and expect [OK]

Hint: Set token, reload, then check with cy.window() and expect [OK]

Common Mistakes:

• Using wrong localStorage property access
• Using non-existent Cypress commands
• Clearing storage instead of verifying token