testdouble/src/object.js

A minimal test double library for TDD with JavaScript

import _ from './wrap/lodash'
import log from './log'
import tdFunction from './function'
import imitate from './imitate'
import proxy from './object/proxy'

const DEFAULT_OPTIONS = { excludeMethods: ['then'] }

export default function object (nameOrType, config) {
  return _.tap(fakeObject(nameOrType, config, arguments.length), (obj) => {
    addToStringToDouble(obj, nameOrType)
  })
}

const fakeObject = function (nameOrType, config, argCount) {
  if (_.isArray(nameOrType)) {
    return createTestDoublesForFunctionNames(nameOrType)
  } else if (_.isObjectLike(nameOrType)) {
    return imitate(nameOrType)
  } else if (_.isString(nameOrType) || argCount === 0) {
    return proxy(nameOrType, withDefaults(config))
  } else if (_.isFunction(nameOrType)) {
    ensureFunctionIsNotPassed()
  } else {
    ensureOtherGarbageIsNotPassed()
  }
}

const createTestDoublesForFunctionNames = (names) =>
  _.transform(names, (acc, funcName) => {
    acc[funcName] = tdFunction(`.${String(funcName)}`)
  }, {})

const ensureFunctionIsNotPassed = () =>
  log.error('td.object', 'Functions are not valid arguments to `td.object` (as of testdouble@2.0.0). Please use `td.function()`, `td.constructor()` or `td.instance()` instead for creating fake functions.')

const ensureOtherGarbageIsNotPassed = () =>
  log.error('td.object', `\
To create a fake object with td.object(), pass it a plain object that contains
functions, an array of function names, or (if your runtime supports ES Proxy
objects) a string name.

If you passed td.object an instance of a custom type, consider passing the
type's constructor to \`td.constructor()\` instead.
`)

const withDefaults = (config) =>
  _.extend({}, DEFAULT_OPTIONS, config)

const addToStringToDouble = (fakeObject, nameOrType) => {
  const name = nameOf(nameOrType)
  fakeObject.toString = () => `[test double object${name ? ` for "${name}"` : ''}]`
}

const nameOf = (nameOrType) =>
  _.isString(nameOrType)
    ? nameOrType
    : ''