assertThat(graphAsMutableGraph.addNode(N1)).isTrue();
    assertThat(graph.nodes()).contains(N1);
  }

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

    addNode(N1);
    ImmutableSet<Integer> nodes = ImmutableSet.copyOf(graph.nodes());
    assertThat(graphAsMutableGraph.addNode(N1)).isFalse();

        assertNotNull(response);
    }

    @Test
    public void test_addRole() throws Exception {
        indexItems();

        PopularWordsResponse response = suggester.popularWords().addRole(SuggestConstants.DEFAULT_ROLE).execute().getResponse();

        assertNotNull(response);
    }

    @Test
    public void test_addField() throws Exception {
        indexItems();

        return this;
    }

    /**
     * Adds a role to filter by.
     * @param role The role.
     * @return This builder instance.
     */
    public PopularWordsRequestBuilder addRole(final String role) {
        request.addRole(role);
        return this;
    }

    /**
     * Adds a field to filter by.
     * @param field The field name.
     * @return This builder instance.
     */

        return this;
    }

    /**
     * Adds a role to filter by.
     * @param role The role.
     * @return This builder instance.
     */
    public SuggestRequestBuilder addRole(final String role) {
        request.addRole(role);
        return this;
    }

    /**
     * Adds a field to filter by.
     * @param field The field name.
     * @return This builder instance.
     */

    assertThat(graphAsMutableGraph.addNode(N1)).isTrue();
    assertThat(graph.nodes()).contains(N1);
  }

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

    addNode(N1);
    ImmutableSet<Integer> nodes = ImmutableSet.copyOf(graph.nodes());
    assertThat(graphAsMutableGraph.addNode(N1)).isFalse();

   * element, or at the end of the list if {@code nextSibling} is null. Note: if {@code nextSibling}
   * is specified, it MUST be for a node for the same {@code key}!
   */
  @CanIgnoreReturnValue
  private Node<K, V> addNode(
      @ParametricNullness K key, @ParametricNullness V value, @Nullable Node<K, V> nextSibling) {
    Node<K, V> node = new Node<>(key, value);
    if (head == null) { // empty list
      head = tail = node;

      assertThat(network.adjacentEdges(E12)).containsExactlyElementsIn(adjacentEdges);
    }
  }

  @Override
  @Test
  public void edgesConnecting_checkReturnedSetMutability() {
    addNode(N1);
    addNode(N2);
    Set<String> edgesConnecting = network.edgesConnecting(N1, N2);
    assertThrows(UnsupportedOperationException.class, () -> edgesConnecting.add(E23));
    addEdge(N1, N2, E12);

    mutableNetwork.addNode("A");
    ImmutableNetwork<String, Integer> immutableNetwork = ImmutableNetwork.copyOf(mutableNetwork);

    assertThat(immutableNetwork).isNotInstanceOf(MutableNetwork.class);
    assertThat(immutableNetwork).isEqualTo(mutableNetwork);

    mutableNetwork.addNode("B");
    assertThat(immutableNetwork).isNotEqualTo(mutableNetwork);
  }

  @Test

    mutableValueGraph.addNode("A");
    ImmutableValueGraph<String, Integer> immutableValueGraph =
        ImmutableValueGraph.copyOf(mutableValueGraph);

    assertThat(immutableValueGraph).isNotInstanceOf(MutableValueGraph.class);
    assertThat(immutableValueGraph).isEqualTo(mutableValueGraph);

    mutableValueGraph.addNode("B");
    assertThat(immutableValueGraph).isNotEqualTo(mutableValueGraph);

        assertNotNull(response);
    }

    @Test
    public void test_addRole() throws Exception {
        indexItems();

        SuggestResponse response = suggester.suggest().setQuery("test").addRole(SuggestConstants.DEFAULT_ROLE).execute().getResponse();

        assertNotNull(response);
        assertEquals(1, response.getNum());
    }

    @Test
    public void test_addField() throws Exception {