graph.putEdge(i, i + 1);
      }
    }
    assertThat(hasCycle(directedNetwork)).isFalse();
    assertThat(hasCycle(undirectedNetwork)).isFalse();
  }

  @Test
  public void hasCycle_twoParallelEdges() {
    for (MutableNetwork<Integer, String> network : networksToTest) {
      network.addEdge(1, 2, "1-2a");
      network.addEdge(1, 2, "1-2b");
    }
    assertThat(hasCycle(directedNetwork)).isFalse();