Flow to gen

Transforms flow type aliases into generators for property based testing

Motivation

This Babel plugin attempts to alleviate the manual task of creating and maintaining fixtures/mocks by transforming all Flowtype type aliases into generator functions for mock data. Additionally, it provides a framework for automatically generating random input for typed functions and React components. If you're unfamiliar with generative or property based testing, please check out an implementation of Quickcheck in your language of choice. Also look at testcheck.js which is 100% compatible and wrapped by the runtime of this library.

By running this Babel transform on your code:

• all type aliases are transformed in testcheck.js generators
• all typed functions can immediately retrieve randomly generated inputs
• all typed React components can immediately retrieve randomly generated props

TODO:

• handle TypeofTypeAnnotation
• handle ExistentialTypeAnnotation
• handle recursive types
• handle Flow globally defined types
• handle React components

Demo?

DEMO!

Getting Started

babel-plugin-transform-flow-to-gen transforms your type aliases into functions that create testcheck.js generators.

Usage

import {sample, types} from 'babel-plugin-transform-flow-to-gen/api';

type Person<T> = {
  firstName: string,
  lastName: string,
  age: T
}

// use the generator static member to create samples
const personGen = Person(types.number());
sample(personGen, 20);
// [{
//   "firstName": "9OY3o",
//   "lastName": "fB",
//   "age": 0
// },
// {
//   "firstName": "8Hft5LwfK",
//   "lastName": "51Vnn54vb9xHO",
//   "age": 2
// },
// {
//   "firstName": "7i59Sr35GAJiv626uiV",
//   "lastName": "s7GIgEf",
//   "age": 3
// },
// {
//   "firstName": "Mys89F65i36n921",
//   "lastName": "",
//   "age": 1
// }, ...]

function setFirstName(person: Person<number>, firstName: string) {
  // ...
}

// returns an array of args for setFirstName
sample(setFirstName.asGenerator());
// [
//  [{
//   "firstName": "3o",
//   "lastName": "j467DA",
//   "age": 0
//   }, "f02j"]
// , ...]

Installing

yarn add babel-plugin-transform-flow-to-gen

License

MIT