Possible to assign temporary material for whole scene for test render?

Is there a way of applying a temporary material to the whole scene for TEST-render, without affecting the ‘reel’ materials of the objects? Would come in handy for things like checking shadow noise issues of Ambient Occlusion or Ambient Lighting in animations (BI),… or for geometry-only checks …

I know that I can disable Textures in the Render panel, but then I still have different colors applied to the scene objects. And as far as I know, Matcap materials seem to just change the appearance in the 3d viewport, right?

I also know I could try something with Render Layers, but since this isn’t reducing render times for quick tests(post process in the compositor…), it’s not what I 'm looking for.

You can add an override material in the Renderlayers / Layers panel. This will apply this override material to all the objects in the scene

Thank you, that’s exactly what I was looking for!