TypeBox Schema Faker

Generate fake data from TypeBox schemas for testing, prototyping and development.

- TypeBox Schema Faker
- Installation
- Usage
- Basic Usage
- Complex Objects
- Arrays and Unions
- Recursive Schemas
- Configuration Options
- Supported TypeBox Schemas
- API
- fake
- Parameters
- Options
- License

Installation

``bash
bun add -D typebox-schema-faker @sinclair/typebox


or

npm install -D typebox-schema-faker @sinclair/typebox

or

yarn add -D typebox-schema-faker @sinclair/typebox
`

Usage

$3

`ts
import { Type } from '@sinclair/typebox';
import { fake } from 'typebox-schema-faker';

// Simple types
const name = fake(Type.String({ minLength: 3, maxLength: 10 }));
// "JvR"

const age = fake(Type.Integer({ minimum: 18, maximum: 65 }));
// 42

const isActive = fake(Type.Boolean());
// true

// Formatted strings
const email = fake(Type.String({ format: 'email' }));
// "john.doe@example.com"

const uuid = fake(Type.String({ format: 'uuid' }));
// "550e8400-e29b-41d4-a716-446655440000"
`

$3

`ts
const userSchema = Type.Object({
id: Type.String({ format: 'uuid' }),
name: Type.String({ minLength: 2, maxLength: 50 }),
email: Type.String({ format: 'email' }),
age: Type.Integer({ minimum: 18, maximum: 100 }),
isActive: Type.Boolean(),
tags: Type.Array(Type.String(), { minItems: 1, maxItems: 5 }),
metadata: Type.Optional(
Type.Object({
created: Type.Date(),
lastLogin: Type.Optional(Type.Date()),
}),
),
});

const fakeUser = fake(userSchema);
// {
// id: "14b926d2-49da-43d3-95bc-3860cb63c6ef",
// name: "5WEX6epIjCNOLfzYnmYqRCkOJaqVS8L6ZRs",
// email: "john.doe@example.com",
// age: 58,
// isActive: true,
// tags: [ "X" ],
// metadata: undefined
// }
`

$3

`ts
// Arrays with constraints
const numbers = fake(Type.Array(Type.Number(), { minItems: 3, maxItems: 6 }));
// [42.5, 17.8, 93.2, 11.7]

// Union types
const status = fake(Type.Union([Type.Literal('active'), Type.Literal('inactive'), Type.Literal('pending')]));
// "active"

// Tuples
const coordinates = fake(Type.Tuple([Type.Number(), Type.Number()]));
// [51.5074, -0.1278]
`

$3

`ts
const treeNodeSchema = Type.Recursive(
(This) =>
Type.Object({
id: Type.String(),
name: Type.String(),
children: Type.Array(This, { minItems: 0, maxItems: 3 }),
}),
{ $id: 'TreeNode' },
);

const tree = fake(treeNodeSchema);
// {
// id: "abc123",
// name: "Root",
// children: [
// {
// id: "def456",
// name: "Child 1",
// children: [...]
// }
// ]
// }
`

$3

`ts
const options = {
/* Chance (0-1) that optional fields are undefined (default: 0.5) /
probability: 0.7,
/* Maximum recursion depth before stopping generation (default: 3) /
maxDepth: 2,
/* The seed number can be used to generate reproducible values /
seed: 999,
};

const result = fake(schema, options);
`

Supported TypeBox Schemas

| Schema Type | Status | Notes |
| ------------------------ | ------ | ----------------------------------------------------- |
| Type.Any() | ✅ | Generates random primitive types, objects, arrays |
| Type.Array() | ✅ | Respects minItems, maxItems constraints |
| Type.BigInt() | ✅ | Supports minimum, maximum constraints |
| Type.Boolean() | ✅ | Generates true/false values |
| Type.Date() | ✅ | Supports minimumTimestamp, maximumTimestamp |
| Type.Function() | ✅ | Returns function that generates fake return values |
| Type.Integer() | ✅ | Supports minimum, maximum constraints |
| Type.Intersect() | ✅ | Merges properties from multiple object schemas |
| Type.Literal() | ✅ | Returns exact literal value |
| Type.Never() | ✅ | Throws TypeBoxError (as expected) |
| Type.Null() | ✅ | Returns null |
| Type.Number() | ✅ | Supports minimum, maximum, multipleOf |
| Type.Object() | ✅ | Generates all properties, handles nesting |
| Type.Optional() | ✅ | Conditionally generates undefined |
| Type.Promise() | ✅ | Returns Promise resolving to fake data |
| Type.Readonly() | ✅ | Freezes generated objects |
| Type.Record() | ✅ | Generates object with dynamic keys/values |
| Type.Recursive() | ✅ | Handles recursive schemas with depth limiting |
| Type.RegExp() | ✅ | Generates strings matching regex patterns |
| Type.String() | ✅ | Supports formats: email, uuid, url, date-time |
| Type.Symbol() | ✅ | Generates unique symbols with descriptions |
| Type.TemplateLiteral() | ✅ | Generates strings matching template patterns |
| Type.This() | ✅ | Resolves recursive references |
| Type.Tuple() | ✅ | Fixed-length arrays with typed elements |
| Type.Uint8Array() | ✅ | Supports minByteLength, maxByteLength |
| Type.Undefined() | ✅ | Returns undefined |
| Type.Union() | ✅ | Randomly selects from union members |
| Type.Unknown() | ✅ | Generates various primitive types (no undefined) |
| Type.Void() | ✅ | Returns undefined |
| Type.Enum() | ✅ | Selects random enum value |
| Type.Ref() | ❌ | Not yet implemented |
| Type.Transform() | ❌ | Not yet implemented |
| Type.Unsafe() | ❌ | Not yet implemented |

API

$3

Signature:

`ts
function fake(schema: T, options: Partial = {}): Static;
`

Generates fake data matching the provided TypeBox schema.

#### Parameters

- schema: TypeBox schema to generate data for
- options: Optional configuration object

#### Options

`ts
export interface FakerOptions {
/* Chance (0-1) that optional fields are undefined (default: 0.5) /
probability: number;
/* Maximum recursion depth before stopping generation (default: 3) /
maxDepth: number;
/* The seed number can be used to generate reproducible values /
seed?: number;
}
``

License

MIT