Function.bind specs

Function.bind.js

// New:

describe('Function.bind', function(){

	it('should still be possible to use it as constructor', function(){
		function Alien(type) {
			this.type = type;
		}

		var thisArg = {};
		var Tribble = Alien.bind(thisArg, 'Polygeminus grex');

		// `thisArg` should **not** be used for the `this` binding when called as a constructor
		var fuzzball = new Tribble('Klingon');
		expect(fuzzball.type).toEqual('Polygeminus grex');
	});

	it('when using .call(thisArg) on a bound function, it should ignore the thisArg of .call', function(){
		var fn = function(){
			return [this.foo].concat(Array.slice(arguments));
		};
		
		expect(fn.bind({foo: 'bar'})()).toEqual(['bar'])
		expect(fn.bind({foo: 'bar'}, 'first').call({foo: 'yeah!'}, 'yooo')).toEqual(['bar', 'first', 'yooo']);

		var bound = fn.bind({foo: 'bar'});
		var bound2 = fn.bind({foo: 'yep'});
		var inst = new bound;
		inst.foo = 'noo!!';
		expect(bound2.call(inst, 'yoo', 'howdy')).toEqual(['yep', 'yoo', 'howdy']);
	});

});

// What we already had:

describe('Function.bind', function(){

	it('should return the function bound to an object', function(){
		var spy = jasmine.createSpy();
		var f = spy.bind('MooTools');
		expect(spy).not.toHaveBeenCalled();
		f();
		expect(spy).toHaveBeenCalledWith();
		f('foo', 'bar');
		expect(spy).toHaveBeenCalledWith('foo', 'bar');
	});

	it('should return the function bound to an object with specified argument', function(){
		var binding = {some: 'binding'};
		var spy = jasmine.createSpy().andReturn('something');
		var f = spy.bind(binding, 'arg');

		expect(spy).not.toHaveBeenCalled();
		expect(f('additional', 'arguments')).toEqual('something');
		expect(spy.mostRecentCall.object).toEqual(binding);
	});

	it('should return the function bound to an object with multiple arguments', function(){
		var binding = {some: 'binding'};
		var spy = jasmine.createSpy().andReturn('something');
		var f = spy.bind(binding, ['foo', 'bar']);

		expect(spy).not.toHaveBeenCalled();
		expect(f('additional', 'arguments')).toEqual('something');
		expect(spy.mostRecentCall.object).toEqual(binding);
	});

});