public void RemoveBox()
{
_boxes.RemoveBox(Reward.Five);
Assert.Equal(7, _boxes.CountBoxes());
Assert.Contains(_boxes, box => box.Reward == Reward.Five);
var fiveBox = _boxes.Single(box => box.Reward == Reward.Five);
Assert.Equal(4, fiveBox.Count);
_boxes.RemoveBox(Reward.Hundred);
Assert.Equal(6, _boxes.CountBoxes());
Assert.DoesNotContain(_boxes, box => box.Reward == Reward.Hundred);
}