HTML & CSS: Debugging & Testing
Systematic debugging and testing catch visual regressions before they ship.
Combine browser DevTools, automated checks, and visual tests to keep interfaces stable across changes.
Inspecting with DevTools
- Use Elements panel to live-edit HTML/CSS and trace computed styles.
- Toggle CSS classes, hover states, and pseudo-classes to debug interactions.
- View layout overlays (box model, flexbox, grid) to diagnose alignment issues.
Note
The Elements panel shows exactly what the browser renders, so you can experiment safely before changing real files.
Linting & formatting
- Configure linters (Stylelint, ESLint) to enforce consistent patterns.
- Use Prettier or editor formatters to maintain readable code.
- Automate lint checks in CI to catch issues before merge.
Note
A linter reviews your code automatically and points out mistakes or style problems.
Automated testing
- Component/unit tests verify behavior of interactive widgets (e.g., Jest, Testing Library).
- Integration tests use tools like Cypress or Playwright for end-to-end flows.
- Visual regression tests (Chromatic, Percy, Happo) detect unintended styling changes.
Note
Visual regression tests compare screenshots; if something moves or changes color unexpectedly, they alert you.
Manual QA
- Test across browsers (Chrome, Edge, Firefox, Safari) and devices.
- Check accessibility with keyboard navigation and screen readers.
- Document test plans for key features and regression suites.