Object factories for testing in TypeScript

Usage no npm install needed!

<script type="module">
  import cookyCutter from '';


🍪 cooky-cutter

Simple, type safe* object factories for JavaScript tests. (*with TypeScript)

Travis branch Coverage Status npm npm type definitions

Read the Release Annoucement.

The problem

You need to write maintainable tests for JavaScript. The code depends on specific entity types defined in the data model. These entities might initially get stubbed out in tests (Mocha, Jest, etc) as plain objects. As complexity grows, you move to factory functions (or another package that does this) to avoid the duplication. A new column gets added, an old one gets removed or maybe an entirely new entity is added. The breaking change isn't noticed until the entire test suite runs (or maybe never).

The solution

cooky-cutter is a light package that leverages TypeScript to define and create factories. Simply pass the type as a generic (assuming you already have a type or interface defined for each entity type). Whenever the entity type changes, the factories become invalid!


npm install --save-dev cooky-cutter
# or
yarn add --dev cooky-cutter

Basic Usage

For more documentation and examples, read the full documentation.

import { define, random, sequence } from "cooky-cutter";

// Define an interface (or type) for the entity
interface User {
  id: number;
  firstName: string;
  lastName: string;
  age: number;

// Define a factory that represents the defined interface
const user = define<User>({
  id: random,
  firstName: i => `Bob #${i}`,
  lastName: "Smith",
  age: sequence

// Invoke the factory a few times
// => { id: 980711200, firstName: 'Bob #1', lastName: 'Smith', age: 1 }

// => { id: 1345667839, firstName: 'Bob #2', lastName: 'Smith', age: 2 }

// => { id: 796816401, firstName: 'Bob #3', lastName: 'Smith', age: 3 }