edges=[('A', 'B'), ('B', 'A'), ('B', 'C'), ('C', 'D'), ('E', 'F')]
kahn_done=['E', 'F']; leftovers=['A', 'B', 'C', 'D']
actual_cycle_members=['A', 'B']; blocked_descendants=['C', 'D']
graphlib_cycle_error=True; still_processed=['E', 'F']
directed_graphs_checked=512; self_loops=included; invalid_inputs=4
PASS: reachability oracle, dependency order and real graphlib agree
