@Test
  public void removeNode_existingNode() {
    assume().that(graphIsMutable()).isTrue();

    putEdge(N1, N2);
    putEdge(N4, N1);
    assertThat(graphAsMutableGraph.removeNode(N1)).isTrue();
    assertThat(graphAsMutableGraph.removeNode(N1)).isFalse();
    assertThat(graph.nodes()).containsExactly(N2, N4);

    assertThat(graph.adjacentNodes(N2)).isEmpty();
    assertThat(graph.predecessors(N2)).isEmpty();

  @Test
  public void removeNode_existingNode() {
    assume().that(graphIsMutable()).isTrue();

    putEdge(N1, N2);
    putEdge(N4, N1);
    assertThat(graphAsMutableGraph.removeNode(N1)).isTrue();
    assertThat(graphAsMutableGraph.removeNode(N1)).isFalse();
    assertThat(graph.nodes()).containsExactly(N2, N4);

    assertThat(graph.adjacentNodes(N2)).isEmpty();
    assertThat(graph.predecessors(N2)).isEmpty();

  /**
   * Removes the specified node from the linked list. This method is only intended to be used from
   * the {@code Iterator} classes. See also {@link LinkedListMultimap#removeAllNodes(Object)}.
   */
  private void removeNode(Node<K, V> node) {
    if (node.previous != null) {
      node.previous.next = node.next;
    } else { // node was head
      head = node.next;
    }
    if (node.next != null) {

    assume().that(graphIsMutable()).isTrue();
    assume().that(network.allowsSelfLoops()).isTrue();

    addNode(N1);
    addEdge(N1, N1, E11);
    assertThat(networkAsMutableNetwork.removeNode(N1)).isTrue();
    assertThat(network.nodes()).isEmpty();
    assertThat(network.edges()).doesNotContain(E11);
  }

  @Test
  public void removeEdge_existingSelfLoopEdge() {