CSF: Add Storybook test syntax (Storybook v10)

[yannbf]

Closes #32244

What I did

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

Follow the documentation here:
https://chromatic-ui.notion.site/Storybook-test-syntax-in-CSF-2566e816203480cb95ddc674ddfbf5d3?pvs=74

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli-storybook/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This pull request has been released as version 0.0.0-pr-32455-sha-5e1c0619. Try it out in a new sandbox by running npx [email protected] sandbox or in an existing project with npx [email protected] upgrade.

More information

Published version	0.0.0-pr-32455-sha-5e1c0619
Triggered by	@yannbf
Repository	storybookjs/storybook
Branch	feature/test-syntax-in-csf-sb10
Commit	5e1c0619
Datetime	Wed Sep 24 08:15:30 UTC 2025 (1758701730)
Workflow run	17970662325

To request a new release of this pull request, mention the @storybookjs/core team.

core team members can create a new canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=32455

Greptile Summary

Updated On: 2025-09-15 09:49:43 UTC

This PR implements a major new feature for Storybook v10: CSF .test syntax that allows developers to write component tests using a familiar, Jasmine-like syntax directly within their story files. The implementation introduces a hierarchical story structure where tests can be attached to stories using a story.test() method (e.g., Primary.test('should render', () => {})).

The feature adds comprehensive infrastructure changes including:

• Type System Updates: New subtype field distinguishes between regular stories (subtype: 'story') and test entries (subtype: 'test'), with API_TestEntry interface and parent-child relationships via parent and parentName fields
• CSF Factories Enhancement: Extended csf-factories.ts with .test() method that creates child stories with test-fn and !autodocs tags, combining parent play functions with test functions
• Story Indexing: Updated indexer to process both story and test entries, creating hierarchical relationships and proper ID generation using toTestId() with colon separator format (storyId:testName)
• UI Integration: Modified sidebar components to support expandable/collapsible stories with children, new TestNode component with beaker icons, and enhanced tag filtering with inclusion/exclusion logic
• Vitest Integration: Added transformer support for generating nested describe/test blocks and enhanced test utilities for executing individual story tests
• Telemetry: Added metrics collection for test usage patterns including test counts per story and adoption statistics

The implementation maintains full backward compatibility while enabling a more organized testing workflow where tests are co-located with stories and displayed as expandable groups in the sidebar. Documentation has been updated to reference @latest instead of @next, indicating preparation for stable release.

Confidence score: 2/5

• This PR introduces complex new functionality but contains several critical issues that could cause immediate problems in production
• Score reflects the presence of duplicate function definitions, malformed URLs, and potential console logging that needs cleanup before merge
• Pay close attention to scripts/tasks/sandbox-parts.ts (duplicate function), URL construction bugs in CLI migration files, and console.log statements in StoryStore.ts

Summary by CodeRabbit

• New Features
  • Add experimental test syntax: define tests on stories, run in Vitest, and deep-link to individual tests.
  • Sidebar support for test items with dedicated icons, keyboard navigation, and status aggregation.
  • Revamped Tag filters: include/exclude modes, presets, and built-in filters (Documentation, Play, Testing).
  • Story index enriched with subtype and parent linkage; improved search and rendering of test entries.
• Bug Fixes
  • Stability and typing improvements in navigation, status calculation, and story extraction.
• Documentation
  • Updated init/upgrade commands to use latest; refined Vitest config examples; removed legacy TOC script.
• Chores
  • Templates and configs enable experimentalTestSyntax by default in supported setups.