A thing to debug my printerbot's bridging problems.
A variety of shapes on two different layers - otherwise it tries bridging the whole thing in one go.

Printing this has been somewhat enlightening. There seems to be a problem bridging to a single layer wall.

Bridgetest2.stl has several wall thickness and heights.
The bridges are all at the same height and Slic3r spans the lot in one pass.

If you have a gcode viewer such as the one in repetier it can be interesting to see what the slicer does.