Porsche oldCar = new Porsche();
oldCar.setMake("Porsche");
oldCar.setColor("white");
oldCar.setModel("GT2000");
oldCar.setYear("2000");
Porsche newCar = (Porsche)dealer.tradeIn(oldCar);
assertNotNull(newCar);
if (newCar != null && "Porsche".equals(newCar.getMake())
&& "911GT3".equals(newCar.getModel())
&& "2007".equals(newCar.getYear())