HTML and CSS Debugging & Testing
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.