Simple check if Image created and setup properly with Jest and Jasmine

test.js

describe('simple test', function() {

    var obj = {
        create_image: function() {
            var image = new Image();
            image.src = 'http://google.com/1x1.gif';
        }
    }

    it('should create image', function() {
        var old_image = global.Image,
            image_src = '';

        var image = function() {
            this.src = '';
        };

        Object.defineProperty(image.prototype, "src", {
            set: function(src) {
                image_src = src;
            }
        });

        global.Image = image;

        obj.create_image();

        expect(image_src).toEqual('http://google.com/1x1.gif');

        global.Image = old_image;

    });
});