var Gallery = function() { this.timeout = 3000; }; Gallery.prototype.setTimeout = function(num) { this.timeout = num; }; var myGallery = new Gallery(); myGallery.setTimeout(5000); var otherGallery = new Gallery(); otherGallery.setTimeout(1000); describe("myGallery", function() { it("does not copy setTimeout", function() { expect(myGallery.hasOwnProperty("setTimeout")).toBe(false); }); it("has a timeout of 5000", function() { expect(myGallery.timeout).toEqual(5000); }); }); describe("otherGallery", function() { it("does not copy setTimeout", function() { expect(myGallery.hasOwnProperty("setTimeout")).toBe(false); }); it("has a timeout of 1000", function() { expect(otherGallery.timeout).toEqual(1000); }); });