Visual regression testing concept in Cypress

Introduction

Visual regression testing helps catch unexpected changes in how a website or app looks. It makes sure the design stays the same after updates.

After changing website styles or layouts to check nothing broke visually.

When adding new features that might affect page appearance.

Before releasing updates to ensure consistent user experience.

To compare current page look with a saved correct version.

When fixing bugs that might impact the design or layout.

Syntax

Cypress

cy.visit('url')
cy.matchImageSnapshot('snapshotName')

cy.visit() loads the page you want to test.

cy.matchImageSnapshot() compares the current page screenshot with a saved image.

Examples

Visit the homepage and check if it looks the same as the saved 'homepage' snapshot.

Cypress

cy.visit('https://example.com')
cy.matchImageSnapshot('homepage')

Test the login page appearance against its saved snapshot.

Cypress

cy.visit('https://example.com/login')
cy.matchImageSnapshot('login-page')

Sample Program

This test opens the Cypress example site homepage and compares its screenshot to the saved 'homepage' image to find visual differences.

Cypress

describe('Visual Regression Test', () => {
  it('checks homepage appearance', () => {
    cy.visit('https://example.cypress.io')
    cy.matchImageSnapshot('homepage')
  })
})

Important Notes

Make sure to save the initial snapshots when running tests for the first time.

Small differences like fonts or colors can cause test failures; adjust thresholds if needed.

Visual regression tests complement, but do not replace, functional tests.

Summary

Visual regression testing checks if a page looks the same after changes.

It uses screenshots compared to saved images called snapshots.

Cypress commands cy.visit() and cy.matchImageSnapshot() help run these tests easily.