* <p><b>Nodes must be unique</b>, just as {@code Map} keys must be. They must also be non-null.
   *
   * @return {@code true} if the network was modified as a result of this call
   */
  @CanIgnoreReturnValue
  boolean addNode(N node);

  /**
   * Adds {@code edge} connecting {@code nodeU} to {@code nodeV}.
   *
   * <p>If the graph is directed, {@code edge} will be directed in this graph; otherwise, it will be
   * undirected.
   *

        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 {

 * SuggestRequest suggestRequest = new SuggestRequest();
 * suggestRequest.setIndex("my_index");
 * suggestRequest.setQuery("example query");
 * suggestRequest.setSize(5);
 * suggestRequest.addTag("tag1");
 * suggestRequest.addRole("role1");
 * suggestRequest.addField("field1");
 * suggestRequest.addKind("kind1");
 * suggestRequest.addLang("en");
 * suggestRequest.setSuggestDetail(true);
 * suggestRequest.setReadingConverter(new MyReadingConverter());

      assertThat(network.nodes()).isEmpty();
      assertThat(network.edges()).isEmpty();
      AbstractNetworkTest.validateNetwork(network);

      while (network.nodes().size() < NUM_NODES) {
        network.addNode(gen.nextInt(NODE_POOL_SIZE));
      }
      ArrayList<Integer> nodeList = new ArrayList<>(network.nodes());
      for (int i = 0; i < NUM_EDGES; ++i) {
        // Parallel edges are allowed, so this should always succeed.

    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  @Test
  public void equivalent_nodeSetsDiffer() {
    network.addNode(N1);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addNode(N2);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {

    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  @Test
  public void equivalent_nodeSetsDiffer() {
    network.addNode(N1);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addNode(N2);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {

    directedGraph.putEdge(N2, N3);
    directedGraph.addNode(N4);

    // the above graph is its own transitive closure
    MutableGraph<Integer> expectedClosure = GraphBuilder.directed().allowsSelfLoops(true).build();
    expectedClosure.putEdge(N1, N2);
    expectedClosure.putEdge(N1, N3);
    expectedClosure.putEdge(N2, N3);
    expectedClosure.addNode(N4);

    assertThat(

     */
    public void addTag(final String tag) {
        tags.add(tag);
    }

    /**
     * Adds a role to filter by.
     * @param role The role.
     */
    public void addRole(final String role) {
        roles.add(role);
    }

    /**
     * Adds a field to filter by.
     * @param field The field name.
     */
    public void addField(final String field) {

    }

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

        PopularWordsResponse response = suggester.popularWords().setSize(10).addRole(SuggestConstants.DEFAULT_ROLE).execute().getResponse();

        assertNotNull(response);
        assertTrue(response.getTotal() > 0);
    }

    @Test
    public void test_addField() throws Exception {

                stream(baseTags).of(stream -> stream.forEach(tag -> popularWordsRequestBuilder.addTag(tag)));
                stream(baseRoles).of(stream -> stream.forEach(role -> popularWordsRequestBuilder.addRole(role)));
                stream(baseFields).of(stream -> stream.forEach(field -> popularWordsRequestBuilder.addField(field)));