Juniper Arbitrary

npm · Source · Changelog

Generate test values from a Juniper schema, typed by it and always valid against it.

import * as fc from 'fast-check';
import { numberSchema, objectSchema, stringSchema } from 'juniper';
import { makeArbitrary } from 'juniper-arbitrary';

const user = objectSchema({
    properties: {
        email: stringSchema().format('email'),
        age: numberSchema().type('integer').minimum(0),
    },
    required: ['email'],
});

fc.assert(
    fc.property(makeArbitrary(user), value => {
        console.log(value);
                    
value: {
    email: string;
    age?: number;
}
    })
);

Get started →

Features

• Valid by construction, then checked: Generators aim at each keyword, and a validator has the last word, so a value that comes out always validates.
• Typed by the schema: An Arbitrary of the schema's SchemaType, with no type to write by hand.
• Fails loudly: A schema nothing matches throws with the path to the part responsible, where a plain .filter() would hang.
• Plain JSON: Values survive a JSON round trip unchanged, with no -0, undefined or null-prototype objects.

Related

Packages

• Juniper

  Build JSON Schemas in TypeScript with inferred static types — strict, Ajv-ready, JSON Schema 2020-12 and OpenAPI 3.0 output.

• Juniper Validator

  Standard Schema compliant validators for Juniper schemas, with type guards and assertions.

Used in demos

• OpenAPI

  A notes API from spec to database: an OpenAPI 3.1 document built from Juniper schemas, genever types for a typed client and a Hono server that validates every request and response, and Drizzle on Postgres with a database per test.