Storybook provides a sandbox to build UIs in isolation so you can develop hard-to-reach states and edge cases. Implement components and pages without needing to fuss with data, APIs, or business logic. Render components in key states that are tricky to reproduce in an app. Save use cases as stories in plain JavaScript to revisit during development, testing, and QA. Use addons to customize your workflow, automate testing, and integrate with your favorite tools. Stories are a pragmatic, reproducible way to keep track of UI edge cases. Write stories once then reuse them to power automated tests. Whenever you write a story you get a handy test case. Quickly browse stories to make sure your UI looks right. Pinpoint UI changes down to the pixel by comparing image snapshots of stories. Reuse stories in your unit tests to confirm nuanced functionality. Stories show how UIs actually work not just how they're supposed to work. That makes gathering feedback and reproductions easy.