In animation world, the "pencil test" has a less interesting but crucial meaning. Basically, it means that you shoot the pencilled frames (on film or video tape) and see how well your animation works - this before you start the hard, challenging and thankless job of inking and coloring the frames.
In digital world, the nearest equivalent is previewing the animation before the final steps. In 3D animation, similar effect can be done by rendering only wireframes or Gouraud-shaded version of the animation before you throw in textures, lighting, shadows and all that...