assertThat(graph.incidentEdgeOrder()).isEqualTo(ElementOrder.stable());
  }

  @Test
  public void immutableGraphBuilder_addNode() {
    ImmutableGraph<String> graph = GraphBuilder.directed().<String>immutable().addNode("A").build();

    assertThat(graph.nodes()).containsExactly("A");
    assertThat(graph.edges()).isEmpty();
  }

  @Test
  public void immutableGraphBuilder_putEdgeFromNodes() {

 *
 * <h3>Usage</h3>
 *
 * Given an algorithm, for example:
 *
 * {@snippet :
 * public <N> someGraphAlgorithm(N startNode, PredecessorsFunction<N> predecessorsFunction);
 * }
 *
 * you will invoke it depending on the graph representation you're using.
 *
 * <p>If you have an instance of one of the primary {@code common.graph} types ({@link Graph},
 * {@link ValueGraph}, and {@link Network}):
 *
 * {@snippet :

  /** Constructor for use by subclasses. */
  public AbstractGraph() {}

  @Override
  public final boolean equals(@Nullable Object obj) {
    if (obj == this) {
      return true;
    }
    if (!(obj instanceof Graph)) {
      return false;
    }
    Graph<?> other = (Graph<?>) obj;

    return isDirected() == other.isDirected()
        && nodes().equals(other.nodes())

 */

package com.google.common.graph;

import java.util.Set;

/**
 * A non-public interface for the methods shared between {@link Graph} and {@link ValueGraph}.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 */
interface BaseGraph<N> extends ArchetypeGraph<N> {
  //
  // Graph-level accessors
  //

  /** Returns all edges in this graph. */
  Set<EndpointPair<N>> edges();

  /**

    assertThat(graph.nodeOrder().comparator()).isEqualTo(Ordering.natural());
    assertThat(graph.nodes()).containsExactly(node2, node4, node6, node8).inOrder();
  }

  private static void addNodes(MutableGraph<Integer> graph) {
    graph.addNode(3);
    graph.addNode(1);
    graph.addNode(4);
  }

  private static void addEdges(MutableNetwork<Integer, String> network) {
    network.addEdge(3, 1, "i");

      MutableGraph<Integer> graph = graphBuilder.allowsSelfLoops(true).build();

      assertThat(graph.nodes()).isEmpty();
      assertThat(graph.edges()).isEmpty();
      AbstractGraphTest.validateGraph(graph);

      while (graph.nodes().size() < NUM_NODES) {
        graph.addNode(gen.nextInt(NODE_POOL_SIZE));
      }
      ArrayList<Integer> nodeList = new ArrayList<>(graph.nodes());

   *
   * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be
   * undirected.
   *
   * <p>If this graph is directed, {@code endpoints} must be ordered.
   *
   * <p>Values do not have to be unique. However, values must be non-null.
   *
   * <p>If either or both endpoints are not already present in this graph, this method will silently

    graph.putEdge("a", "b");

    Traverser.forTree(graph); // Does not throw
  }

  @Test
  public void forTree_withUndirectedGraph_throws() throws Exception {
    MutableGraph<String> graph = GraphBuilder.undirected().build();
    graph.putEdge("a", "b");

    assertThrows(IllegalArgumentException.class, () -> Traverser.forTree(graph));
  }

  @Test
  @SuppressWarnings("CheckReturnValue")

  final N node;
  final ArchetypeGraph<N> graph;
  final EdgeType edgeType;

  enum EdgeType {
    INCOMING, // incoming incident edges only
    OUTGOING, // outgoing incident edges only
    BOTH // both incoming and outgoing incident edges
  }

  IncidentEdgeSet(ArchetypeGraph<N> graph, N node, EdgeType edgeType) {
    this.graph = graph;
    this.node = node;
    this.edgeType = edgeType;
  }

        }

        if (graph.isEmpty()) {
            throw new GraphConflictResolutionException("graph with an entry, but not vertices do not exist");
        }

        if (graph.isEmptyEdges()) {
            return null; // no edges - nothing to worry about
        }

        final TreeSet<MetadataGraphVertex> vertices = graph.getVertices();

        try {
            // edge case - single vertex graph