//
  // Graph properties
  //

  /**
   * Returns true if the edges in this graph are directed. Directed edges connect a {@link
   * EndpointPair#source() source node} to a {@link EndpointPair#target() target node}, while
   * undirected edges connect a pair of nodes to each other.
   */
  boolean isDirected();

  /**
   * Returns true if this graph allows self-loops (edges that connect a node to itself). Attempting

  private ValueGraphBuilder(boolean directed) {
    super(directed);
  }

  /** Returns a {@link ValueGraphBuilder} for building directed graphs. */
  public static ValueGraphBuilder<Object, Object> directed() {
    return new ValueGraphBuilder<>(true);
  }

  /** Returns a {@link ValueGraphBuilder} for building undirected graphs. */
  public static ValueGraphBuilder<Object, Object> undirected() {

   *     false, creates an instance for graphs whose edges are each undirected.
   */
  AbstractGraphBuilder(boolean directed) {
    this.directed = directed;
  }

  private final EdgeType edgeType;
  private final MutableGraph<Integer> graph;

  // add parameters: directed/undirected
  @Parameters
  public static Collection<Object[]> parameters() {
    return Arrays.asList(new Object[][] {{EdgeType.UNDIRECTED}, {EdgeType.DIRECTED}});
  }

  public GraphEquivalenceTest(EdgeType edgeType) {
    this.edgeType = edgeType;
    this.graph = createGraph(edgeType);
  }

import java.util.Collection;
import org.jspecify.annotations.NullUnmarked;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

/** Tests for an undirected {@link StandardMutableGraph}. */
@AndroidIncompatible
@RunWith(Parameterized.class)
@NullUnmarked
public final class StandardImmutableUndirectedGraphTest
    extends AbstractStandardUndirectedGraphTest {

  /**
   * Add {@code node} as a predecessor to the origin node. In the case of an undirected graph, it
   * also becomes a successor. Associates {@code value} with the edge connecting the two nodes.
   */
  void addPredecessor(N node, V value);

  /**
   * Add {@code node} as a successor to the origin node. In the case of an undirected graph, it also

  /**
   * Adds {@code edge} connecting {@code endpoints}. In an undirected network, {@code edge} will
   * also connect {@code nodeV} to {@code nodeU}.
   *
   * <p>If this graph is directed, {@code edge} will be directed in this graph; if it is undirected,
   * {@code edge} will be undirected in this graph.
   *
   * <p>If this graph is directed, {@code endpoints} must be ordered.
   *

  //
  // ValueGraph properties
  //

  /**
   * Returns true if the edges in this graph are directed. Directed edges connect a {@link
   * EndpointPair#source() source node} to a {@link EndpointPair#target() target node}, while
   * undirected edges connect a pair of nodes to each other.
   */
  @Override
  boolean isDirected();

  /**

  // Node order tests

  @Test
  public void nodeOrder_none() {
    MutableGraph<Integer> graph = GraphBuilder.directed().nodeOrder(unordered()).build();

    assertThat(graph.nodeOrder()).isEqualTo(unordered());
  }

  @Test
  public void nodeOrder_insertion() {
    MutableGraph<Integer> graph = GraphBuilder.directed().nodeOrder(insertion()).build();

    addNodes(graph);

    assertThat(graph.nodeOrder()).isEqualTo(insertion());

    assertThat(toString).contains("valueD");
  }

  @Test
  public void undirectedGraph() {
    graph = ValueGraphBuilder.undirected().allowsSelfLoops(true).build();
    graph.putEdgeValue(1, 2, "valueA");
    graph.putEdgeValue(2, 1, "valueB"); // overwrites valueA in undirected case
    graph.putEdgeValue(2, 3, "valueC");
    graph.putEdgeValue(4, 4, "valueD");