public void Write_To_Stream() { //arrange var stream = new StringStream(); var order = new WalkDogOrder(new Dog("Santa's Little Helper", true, false), "Springfield", new DateTime(2017, 03, 17), 17.89); var writer = new WalkDogOrderStreamWriter(); //act writer.Write(stream, order); //assert var content = stream.GetContent(); content.Should().Be("Santa's Little Helper (small) in Springfield at 2017-03-17T00:00:00.0000000 for 17.89$"); }