Type Mock Data and Test Fixtures

Generate TypeScript interfaces from JSON mock data and test fixtures to type your unit tests and Storybook stories.

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Root interface name

JSON input

TypeScript output

export interface User {
  id: number;
  name: string;
  email: string;
  isActive: boolean;
  score: number;
  tags: string[];
  address?: null;
}

export interface Root {
  user: User;
  createdAt: string;
  version: number;
}

Testing tips

🧪

Paste your mock JSON fixture and generate an interface. Import it in your test files so TypeScript validates mock shape matches the real API contract.

💡

Storybook args are more maintainable when typed. Generate an interface from your component's mock props JSON and use it as the Args type for your stories.

🔍

Mismatches between mock data and real API shape are a common source of test false positives. Strong typing from generated interfaces catches these at build time.

⚡

When your API contract changes, update the mock JSON and regenerate the interface. TypeScript will then flag all usages that need updating — instant impact assessment.