graph.putEdge(2, 3);
      graph.putEdge(3, 1);
    }
    assertThat(hasCycle(directedGraph)).isTrue();
    assertThat(hasCycle(undirectedGraph)).isTrue();
  }

  @Test
  public void hasCycle_deepPathGraph() {
    for (MutableGraph<Integer> graph : graphsToTest) {
      for (int i = 0; i < 100000; i++) {
        graph.putEdge(i, i + 1);
      }
    }
    assertThat(hasCycle(directedNetwork)).isFalse();