SubgraphStrategyTest contains test cases that access both vertices incident on edges which isn't allowed under GraphComputer semantics. It silently passes in GraphComputerTest because the TP3 implementations ignore those cases. I believe implementations should throw an exception on such access. This example demonstrates how easy it is to end up with difficult to find bugs otherwise. We would put a high burden on the user to write unit tests for their strategies to make sure they detect those cases where it makes a difference.
Moreover, we should think about such FilterStrategies in general. Should there be a way to restrict them to just stargraph access to ensure that they always work in GraphComputer? Basically, I think it would be great to avoid a case where a strategy works in OLTP but doesn't in OLAP because most people would probably implement it for OLTP first. This is particularly true for SubgraphStrategies where you try to restrict access. WDYT? Matthias
