public void TestPush()
{
var turtle = new Turtle(new Vector(0, 0), 0.0, ImmutableStack<Turtle.TurtleState>.Empty, dummy, Colors.Black);
var pushed = turtle.Push();
var first = pushed.Stack.Peek();
var pos = first.Position;
var angle = first.Angle;
var color = first.DrawColor;
Assert.AreEqual(turtle.Position, pos);
Assert.AreEqual(turtle.Angle, angle);
Assert.AreEqual(turtle.DrawColor, color);
}