Add some tests for sortLayer
Add some tests for sortLayer

tylingsoft/dagre-layout,abduld/dagre,9n/dagre,9n/dagre,abduld/dagre,lmcorbo/dagre,cpettitt/dagre,tylingsoft/dagre-layout,shelsonjava/dagre,abduld/dagre,rwl/dagre,kdawes/dagre,witcxc/dagre,cpettitt/dagre,kdawes/dagre,cpettitt/dagre,GerHobbelt/dagre,shelsonjava/dagre,witcxc/dagre,lmcorbo/dagre,GerHobbelt/dagre,9n/dagre,shelsonjava/dagre,GerHobbelt/dagre,lmcorbo/dagre,kdawes/dagre