[shortscale] added tests for the case of 0
[shortscale] added tests for the case of 0

onaio/plottable,RobertoMalatesta/plottable,gdseller/plottable,iobeam/plottable,alyssaq/plottable,NextTuesday/plottable,iobeam/plottable,danmane/plottable,RobertoMalatesta/plottable,softwords/plottable,palantir/plottable,jacqt/plottable,gdseller/plottable,NextTuesday/plottable,jacqt/plottable,danmane/plottable,palantir/plottable,jacqt/plottable,alyssaq/plottable,palantir/plottable,softwords/plottable,RobertoMalatesta/plottable,onaio/plottable,softwords/plottable,NextTuesday/plottable,onaio/plottable,iobeam/plottable,palantir/plottable,gdseller/plottable,alyssaq/plottable,danmane/plottable