verify-it/src/ScenarioBuilder.js

Randomised test property/data generation for NodeJS

'use strict'

const createFunctionWithCorrectArgsLength = (numberOfArgs, fn) => {
  switch (numberOfArgs) {
    case 0:
      return function () {
        return fn.apply(this, arguments)
      }
    case 1:
      return function (_) {
        return fn.apply(this, arguments)
      }
    case 2:
      return function (_, __) {
        return fn.apply(this, arguments)
      }
    default:
      throw new Error(
        'Use of more than 2 non-generated scenario arguments is currently unsupported'
      )
  }
}

const ScenarioBuilder = {
  build: (body, generators) => {
    const numberOfScenarioArgs = Math.max(body.length - generators.length, 0)

    const scenario = function () {
      const argumentsArray = [].slice.call(arguments)
      const inputs = generators.map((generator) => generator())
      const bodyArguments = inputs.concat(argumentsArray)
      return body.apply(null, bodyArguments)
    }

    return createFunctionWithCorrectArgsLength(numberOfScenarioArgs, scenario)
  }
}

module.exports = ScenarioBuilder