>>> import extrapolation
>>> import moving

>>> et = extrapolation.ExtrapolatedTrajectoryConstant(moving.Point(0,0), moving.Point(1,0))
>>> et.predictPosition(4) # doctest:+ELLIPSIS
(0.0...,4.0...)
>>> et.predictPosition(1) # doctest:+ELLIPSIS
(0.0...,1.0...)
