Dijkstra on a graph with one negative edge:
  finalize s at d=0
  finalize a at d=2
  finalize b at d=3

vertex | Dijkstra | Bellman-Ford | truth
-------+----------+--------------+-------
   s   |    0     |      0       |   0
   a   |    2     |      1       |   1   <-- Dijkstra is WRONG
   b   |    3     |      3       |   3
