The bfs reducer populates the initial queue by including all vertices who do not appear in the graph's in_edges. This check isn't sufficient for the case where a vertex had an inbound edge, which is then deleted from the graph, leaving an empty set in it's place.
Coverage increased (+0.01%) to 96.057% when pulling a54487d9dae9b57905d060881abe18eab102e516 on QuinnWilton:bfs-inbound-edges into 493d91d214418bbd9607881bb1db270352b27a26 on bitwalker:master.
The bfs reducer populates the initial queue by including all vertices who do not appear in the graph's
in_edges
. This check isn't sufficient for the case where a vertex had an inbound edge, which is then deleted from the graph, leaving an empty set in it's place.