private void AssertUnbound(GarageEntity garage, CarEntity car)
 {
     Assert.NotEqual(garage, car.Garage);
     Assert.False(garage.HasCar(car));
 }
 private void AssertBound(GarageEntity garage, CarEntity car)
 {
     Assert.Equal(garage, car.Garage);
     Assert.True(garage.HasCar(car));
 }