Type Mock Data and Test Fixtures

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

No login required

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.