test.js

/* globals describe,beforeEach,it,xit */
var expect = require('expect')

;['slice', 'concat', 'loop'].forEach(function(bind) {
  describe(bind, function () {
    var actual, expected

    var testSubject = {
      push: function (o) {
        this.a.push(o)
      }
    }

    function func() { //jshint validthis:true
      Array.prototype.forEach.call(arguments, function (a) {
        this.push(a)
      }, this)
      return this
    }

    beforeEach(function () {
      actual = []
      testSubject.a = []
      Function.prototype.bind = require('./bind-' + bind)
    })

    it('binds properly without a context', function () {
      var context
      testSubject.func = function () {
        context = this
      }.bind()
      testSubject.func()
      expect(context).toBe(function () { return this }.call())
    })

    it('binds properly without a context, and still supplies bound arguments', function () {
      var a, context
      testSubject.func = function () {
        a = Array.prototype.slice.call(arguments)
        context = this
      }.bind(undefined, 1,2,3)
      testSubject.func(1,2,3)
      expect(a).toEqual([1,2,3,1,2,3])
      expect(context).toBe(function () { return this }.call())
    })

    it('binds a context properly', function () {
      testSubject.func = func.bind(actual)
      testSubject.func(1,2,3)
      expect(actual).toEqual([1,2,3])
      expect(testSubject.a).toEqual([])
    })

    it('binds a context and supplies bound arguments', function () {
      testSubject.func = func.bind(actual, 1,2,3)
      testSubject.func(4,5,6)
      expect(actual).toEqual([1,2,3,4,5,6])
      expect(testSubject.a).toEqual([])
    })

    it('returns properly without binding a context', function () {
      testSubject.func = function () {
        return this
      }.bind()
      var context = testSubject.func()
      expect(context).toBe(function () { return this }.call())
    })

    it('returns properly without binding a context, and still supplies bound arguments', function () {
      var context
      testSubject.func = function () {
        context = this
        return Array.prototype.slice.call(arguments)
      }.bind(undefined, 1,2,3)
      actual = testSubject.func(1,2,3)
      expect(context).toBe(function () { return this }.call())
      expect(actual).toEqual([1,2,3,1,2,3])
    })

    it('returns properly while binding a context properly', function () {
      var ret
      testSubject.func = func.bind(actual)
      ret = testSubject.func(1,2,3)
      expect(ret).toBe(actual)
      expect(ret).toNotBe(testSubject)
    })

    it('returns properly while binding a context and supplies bound arguments', function () {
      var ret
      testSubject.func = func.bind(actual, 1,2,3)
      ret = testSubject.func(4,5,6)
      expect(ret).toBe(actual)
      expect(ret).toNotBe(testSubject)
    })

    it('has the new instance\'s context as a constructor', function () {
      var actualContext
      var expectedContext = { foo: 'bar' }
      testSubject.func = function () {
        actualContext = this
      }.bind(expectedContext)
      var result = new testSubject.func()
      expect(actualContext).toNotBe(expectedContext)
    })

    it('passes the correct arguments as a constructor', function () {
      var ret, expected = { name: 'Correct' }
      testSubject.func = function (arg) {
        return arg
      }.bind({ name: 'Incorrect' })
      ret = new testSubject.func(expected)
      expect(ret).toBe(expected)
    })

    it('returns the return value of the bound function when called as a constructor', function () {
      var oracle = [1, 2, 3]
      var Subject = function () {
        return oracle
      }.bind(null)
      var result = new Subject()
      expect(result).toBe(oracle)
    })

    it('returns the correct value if constructor returns primitive', function () {
      var oracle = [1, 2, 3]
      var Subject = function () {
        return oracle
      }.bind(null)
      var result = new Subject()
      expect(result).toBe(oracle)

      oracle = {}
      result = new Subject()
      expect(result).toBe(oracle)

      oracle = function () {}
      result = new Subject()
      expect(result).toBe(oracle)

      oracle = 'asdf'
      result = new Subject()
      expect(result).toNotBe(oracle)

      oracle = null
      result = new Subject()
      expect(result).toNotBe(oracle)

      oracle = true
      result = new Subject()
      expect(result).toNotBe(oracle)

      oracle = 1
      result = new Subject()
      expect(result).toNotBe(oracle)
    })

    it('returns the value that instance of original "class" when called as a constructor', function () {
      var ClassA = function (x) {
        this.name = x || 'A'
      }
      var ClassB = ClassA.bind(null, 'B')

      var result = new ClassB()
      expect(result instanceof ClassA).toBe(true)
      expect(result instanceof ClassB).toBe(true)
    })

    xit('sets a correct length without thisArg', function () {
      var Subject = function (a, b, c) { return a + b + c }.bind()
      expect(Subject.length).toBe(3)
    })

    xit('sets a correct length with thisArg', function () {
      var Subject = function (a, b, c) { return a + b + c }.bind({})
      expect(Subject.length).toBe(3)
    })

    xit('sets a correct length with thisArg and first argument', function () {
      var Subject = function (a, b, c) { return a + b + c }.bind({}, 1)
      expect(Subject.length).toBe(2)
    })

    xit('sets a correct length without thisArg and first argument', function () {
      var Subject = function (a, b, c) { return a + b + c }.bind(undefined, 1)
      expect(Subject.length).toBe(2)
    })

    xit('sets a correct length without thisArg and too many argument', function () {
      var Subject = function (a, b, c) { return a + b + c }.bind(undefined, 1, 2, 3, 4)
      expect(Subject.length).toBe(0)
    })
  })
})