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

// 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

// 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

# 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

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

storybook-testing