public void Movement_Drag()
{
// drag hinders acceleration
_movement.Start(_container);
_movement.Floating = true;
_movement.DragX(0.8f);
_movement.VelocityX = 10;
_container.Tick();
Assert.AreEqual(8, _position.Position.X);
Assert.AreEqual(8, _movement.VelocityX);
_movement.DragX(0.5f);
_movement.VelocityX = -10;
_container.Tick();
// velocity intended to go from 8 to -10, a change of 18.
// drag of 0.5 cuts that down to a change of 9
Assert.AreEqual(7, _position.Position.X);
Assert.AreEqual(-1, _movement.VelocityX);
}