public void CommandFactory_InvalidCommand_Null() { //Arrange Point startingPoint = new Point(0, 0); MarsRover.CardinalDirection startingDirection = MarsRover.CardinalDirection.North; MarsRover rover = new MarsRover(startingPoint, startingDirection, null, null); //Act IRoverCommand cmd = rover.CommandFactory('?'); //Assert Assert.IsNull(cmd); }