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import { bind } from './bind.js'
function Foo(x){  this.x = x}function add(x){  return this.x + x}function Bar(x, y){  this.x = x  this.y = y}Bar.prototype = new Foo()Bar.prototype.getX = function (){  return 'prototype getX'}
test('returns a function', () => {  expect(typeof bind(add)(Foo)).toBe('function')})
test('returns a function bound to the specified context object', () => {  const f = new Foo(12)  function isFoo(){    return this instanceof Foo  }  const isFooBound = bind(isFoo, f)  expect(isFoo()).toBeFalse()  expect(isFooBound()).toBeTrue()})
test('works with built-in types', () => {  const abc = bind(String.prototype.toLowerCase, 'ABCDEFG')  expect(typeof abc).toBe('function')  expect(abc()).toBe('abcdefg')})
test('works with user-defined types', () => {  const f = new Foo(12)  function getX(){    return this.x  }  const getXFooBound = bind(getX, f)  expect(getXFooBound()).toBe(12)})
test('works with plain objects', () => {  const pojso = { x : 100 }  function incThis(){    return this.x + 1  }  const incPojso = bind(incThis, pojso)  expect(typeof incPojso).toBe('function')  expect(incPojso()).toBe(101)})
test('does not interfere with existing object methods', () => {  const b = new Bar('a', 'b')  function getX(){    return this.x  }  const getXBarBound = bind(getX, b)  expect(b.getX()).toBe('prototype getX')  expect(getXBarBound()).toBe('a')})
test('preserves arity', () => {  const f0 = function (){    return 0  }  const f1 = function (a){    return a  }  const f2 = function (a, b){    return a + b  }  const f3 = function (    a, b, c  ){    return a + b + c  }
  expect(bind(f0, {})).toHaveLength(0)  expect(bind(f1, {})).toHaveLength(1)  expect(bind(f2, {})).toHaveLength(2)  expect(bind(f3, {})).toHaveLength(3)})