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