Visual regression testing

Automated screenshots of pages or components compared with approved ones, so unintended visual changes fail the build.

A test runner such as Playwright renders the page in set browsers and screen sizes, takes a screenshot and diffs it against the baseline. A CSS change that breaks a page nobody looked at shows up as a red pixel diff in the pull request. It matters more with coding agents, which edit styles confidently and rarely look at the result.

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Related terms

Design system (Storybook): Shared components, tokens and rules that keep a product consistent across screens, teams and platforms.
Accessibility (a11y): Building software that people with disabilities can use: with a keyboard, a screen reader, zoom or captions.
Coding agent: An agent that reads a repository, edits files, runs commands and tests, and opens pull requests.

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