public void TestLeftCommand()
{
var rover = new Rover();
rover.Stand(new Point(1, 1), Direction.NORTH);
var cmd = new LeftCommand(rover);
Assert.IsTrue(cmd.Validate());
cmd.Execute();
Assert.AreEqual(rover.Position.X, 1);
Assert.AreEqual(rover.Position.Y, 1);
Assert.AreEqual(rover.Direction, Direction.WEST);
}