What is the best way to test a SPA across browsers

The best way to test a SPA across browsers is a layered approach:

1) Use automated cross-browser end-to-end tests

Run your core user journeys in real browsers using a tool like:

• Playwright — strong choice today
• Cypress — good, but cross-browser support is less broad than Playwright
• Selenium/WebDriver — more traditional, widely supported

Why: SPAs often break in browser-specific rendering, timing, routing, or JS API behavior. E2E tests catch those issues best.

What to cover

Focus on critical flows, not every click:

• sign up / login
• navigation/routing
• forms and validation
• API-driven state changes
• file upload/download
• permissions / auth flows
• responsive behavior if relevant

2) Run tests on multiple browser engines

At minimum test:

• Chromium (Chrome / Edge)
• Firefox
• WebKit (Safari-like behavior)

This catches most compatibility issues early.

3) Add device / OS coverage when needed

If your users care about mobile or specific platforms:

• test on real iOS Safari and Android Chrome
• use cloud services like BrowserStack, Sauce Labs, or LambdaTest

4) Combine with unit and integration tests

Use:

• unit tests for components and utilities
• integration tests for component interactions
• E2E tests for full browser behavior

This gives faster feedback and keeps browser testing focused on real user paths.

5) Include visual regression testing

For UI-heavy SPAs, add screenshot/visual diffs to catch:

• layout shifts
• font rendering differences
• CSS regressions
• responsive breakpoints

Tools: Percy, Chromatic, Playwright screenshots

6) Test in CI

Run cross-browser tests in your CI pipeline on every PR or merge.

A common setup:

• quick unit/integration tests on every commit
• cross-browser E2E on main branches or nightly
• full cloud/device matrix before release

Best practical recommendation

If you want the simplest strong setup:

• Playwright
• run against Chromium, Firefox, WebKit
• add BrowserStack for real mobile Safari/Android when needed
• keep tests focused on critical flows
• use screenshot testing for UI regressions

If you want, I can suggest a specific testing stack and CI setup for React, Vue, Angular, or plain JS.