storybook-testing

---
name: storybook-testing
license: MIT
compatibility: "Claude Code 2.1.76+."
description: Storybook 10 testing patterns with Vitest integration, ESM-only distribution, CSF3 typesafe factories, play() interaction tests, Chromatic TurboSnap visual regression, module automocking, accessibility addon testing, and autodocs generation. Use when writing component stories, setting up visual regression testing, configuring Storybook CI pipelines, or migrating from Storybook 9.
tags: [storybook, vitest, csf3, chromatic, turbosnap, visual-regression, play-functions, component-testing, a11y-testing, autodocs, esm-only, module-automocking]
context: fork
agent: frontend-ui-developer
version: 2.0.0
author: OrchestKit
user-invocable: false
disable-model-invocation: true
complexity: medium
persuasion-type: guidance
targets:
  - library: storybook
    version: ">=10.3.0"
metadata:
  category: document-asset-creation
  storybook-version: "10.3"
allowed-tools:
  - Read
  - Glob
  - Grep
  - WebFetch
  - WebSearch
---

# Storybook Testing — Storybook 10

## Overview

Storybook 10 unifies component testing into a single workflow: **interaction tests** via `play()` functions, **visual regression** via Chromatic TurboSnap, and **accessibility audits** via the a11y addon — all running through Vitest. Stories are executable test specifications, not just documentation.

**What's new in Storybook 10** (vs 9):
- **ESM-only enforced** — the single breaking change; Node 20.16+ / 22.19+ / 24+ required; 29% smaller install
- **Module automocking (`sb.mock`)** — build-time module mocking, scoped per-project in preview.ts
- **CSF factories (React, preview)** — `defineMain` → `definePreview` → `preview.meta()` → `meta.story()` chain
- **Essential addons in core** — viewport, controls, interactions, actions no longer separate deps
- **Import path changes** — `@storybook/test` → `storybook/test` (old paths still work as aliases)
- **React Server Component story support** — test RSC in isolation
- **Vitest 4 support** — `experimental-addon-test` renamed to `addon-vitest`

**When to use this skill:**
- Writing component stories in CSF3 format with TypeScript
- Setting up interaction tests with `play()` functions
- Configuring Chromatic visual regression with TurboSnap
- Using module automocking at the story level
- Running accessibility tests in CI via the a11y addon
- Generating living documentation with autodocs
- Migrating from Storybook 9 to 10

---

## Quick Reference

| Rule | Impact | Description |
|------|--------|-------------|
| `storybook-csf3-factories` | HIGH | Typesafe CSF3 story factories with `satisfies Meta` |
| `storybook-play-functions` | CRITICAL | Interaction testing with `play()` and `@storybook/test` |
| `storybook-vitest-integration` | HIGH | Run stories as Vitest tests via `@storybook/addon-vitest` |
| `storybook-chromatic-turbosnap` | HIGH | TurboSnap reduces snapshot cost 60-90% |
| `storybook-sb-mock` | HIGH | Story-level module mocking with `sb.mock` |
| `storybook-a11y-testing` | CRITICAL | Automated axe-core accessibility scans in CI |
| `storybook-autodocs` | MEDIUM | Auto-generated docs from stories |

---

## Storybook Testing Pyramid

```
         ┌──────────────┐
         │   Visual     │  Chromatic TurboSnap
         │  Regression  │  (snapshot diffs)
         ├──────────────┤
         │ Accessibility│  @storybook/addon-a11y
         │   (a11y)     │  (axe-core scans)
         ├──────────────┤
         │ Interaction  │  play() functions
         │   Tests      │  (@storybook/test)
         ├──────────────┤
         │  Unit Tests  │  Vitest + storybookTest
         │  (stories)   │  plugin
         └──────────────┘
```

Each layer catches different defects: unit tests validate logic, interaction tests verify user flows, a11y tests catch accessibility violations, and visual tests catch unintended UI regressions.

---

## Quick Start

### CSF3 Story with Play Function

```tsx
// Button.stories.tsx
import type { Meta, StoryObj } from '@storybook/react'
import { expect, fn, userEvent, within } from 'storybook/test'
import { Button } from './Button'

const meta = {
  component: Button,
  args: {
    onClick: fn(),
  },
} satisfies Meta<typeof Button>

export default meta
type Story = StoryObj<typeof meta>

export const Primary: Story = {
  args: {
    label: 'Click me',
    variant: 'primary',
  },
  play: async ({ canvasElement, args }) => {
    const canvas = within(canvasElement)
    const button = canvas.getByRole('button', { name: /click me/i })

    await userEvent.click(button)
    await expect(args.onClick).toHaveBeenCalledOnce()
    await expect(button).toHaveStyle({ backgroundColor: 'rgb(37, 99, 235)' })
  },
}
```

### Vitest Configuration

```ts
// vitest.config.ts
import { storybookTest } from '@storybook/addon-vitest/vitest-plugin'
import { defineConfig } from 'vitest/config'

export default defineConfig({
  plugins: [storybookTest()],
  test: {
    setupFiles: ['./vitest.setup.ts'],
  },
})
```

---

## Key Principles

- **Stories are tests.** Every story with a `play()` function is an executable interaction test that runs in Vitest.
- **CSF3 + `satisfies` for type safety.** Use `satisfies Meta<typeof Component>` for full type inference on args and play functions.
- **Module automocking (SB 10).** Register `sb.mock(import(...))` in `.storybook/preview.ts`, configure per-story with `mocked()` in `beforeEach`. Never use `vi.mock` in story files. No factory functions — `sb.mock` is build-time, not runtime.
- **TurboSnap for CI speed.** Only snapshot stories affected by code changes — reduces Chromatic usage by 60-90%.
- **Accessibility is not optional.** The a11y addon runs axe-core scans on every story and gates CI on violations.
- **Living documentation.** Autodocs generates prop tables and usage examples directly from stories — no separate docs site needed.

---

## Anti-Patterns (FORBIDDEN)

| Anti-Pattern | Why It Fails | Use Instead |
|-------------|-------------|-------------|
| CSF2 `Template.bind({})` | Deprecated, no type inference, will be removed in SB 11 | CSF3 object stories with `satisfies` |
| `@storybook/test-runner` package | Deprecated since Storybook 9 | `@storybook/addon-vitest` |
| `vi.mock()` in story files | Leaks between stories, breaks isolation | Register `sb.mock(import(...))` in preview.ts, configure with `mocked()` in beforeEach |
| Full Chromatic snapshots on every PR | Expensive and slow | TurboSnap with `onlyChanged: true` |
| Manual accessibility checking | Misses violations, not repeatable | `@storybook/addon-a11y` in CI pipeline |
| Separate documentation site | Drifts from actual component behavior | Autodocs with `tags: ['autodocs']` |
| Testing implementation details | Brittle, breaks on refactors | Test user-visible behavior via `play()` |
| CJS imports in stories | ESM-only since SB 9/10 | Use ESM imports, set `"module": "ESNext"` in tsconfig |

---

## Storybook MCP Integration (addon-mcp)

When `@storybook/addon-mcp` is installed, agents can run tests and preview stories via MCP instead of CLI. This enables the **generate → test → self-heal** loop.

### MCP Tools for Testing

| Tool | Purpose |
|------|---------|
| `run-story-tests` | Run component + a11y tests via MCP, returns pass/fail + violation details |
| `preview-stories` | Returns preview URLs for visual verification in chat |
| `get-storybook-story-instructions` | Guidance on writing effective stories + interaction tests |

### Agent Testing Loop

```python
# 1. Generate component + CSF3 story
# 2. Run tests via MCP
results = run-story-tests(
    stories=[{ "storyId": "button--primary" }],
    a11y=True
)
# 3. If failures: read violations, fix, retry (max 3)
# 4. Preview in chat for visual confirmation
preview-stories(stories=[{ "storyId": "button--primary" }])
```

### Setup

```bash
npx storybook add @storybook/addon-mcp
# Enable docs toolset in .storybook/main.ts:
#   experimentalComponentsManifest: true
npx mcp-add --type http --url "http://localhost:6006/mcp" --scope project
```

See `storybook-mcp-integration` skill for full tool reference and patterns.

---

## References

- `references/storybook-migration-guide.md` — Migration path from Storybook 9 to 10
- `references/storybook-ci-strategy.md` — CI pipeline configuration for visual, interaction, and a11y testing
- `references/storybook-addon-ecosystem.md` — Essential addons for Storybook 10 in 2026

## Related Skills

- `storybook-mcp-integration` — Storybook MCP tools: component discovery, testing, previews
- `react-server-components-framework` — React 19 + Next.js 16 patterns (component architecture)
- `accessibility` — Broader accessibility patterns beyond Storybook
- `devops-deployment` — CI/CD pipeline patterns for automated testing