When doing graph traversal, I first chose a LinkedList to maintain all visited nodes.
But I can't figure out why there would be a false negative test case.

 List<Stmt> isVisited = new LinkedList<>(); ArrayDeque<Stmt> queue = new ArrayDeque<>(); // BFS queue queue.add(cfg.getEntry()); 

Then, if I change to use a HashSet, all test cases will pass.