@Test
  public void hasEdgeConnecting_disconnectedNodes() {
    addNode(N1);
    addNode(N2);
    assertThat(network.hasEdgeConnecting(N1, N2)).isFalse();
  }

  @Test
  public void hasEdgesConnecting_nodesNotInGraph() {
    addNode(N1);
    addNode(N2);
    assertThat(network.hasEdgeConnecting(N1, NODE_NOT_IN_GRAPH)).isFalse();
    assertThat(network.hasEdgeConnecting(NODE_NOT_IN_GRAPH, N2)).isFalse();