}

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test
  public void equivalent_directedVsUndirected() {
    graph.putEdge(N1, N2);

    MutableGraph<Integer> g2 = createGraph(oppositeType(edgeType));
    g2.putEdge(N1, N2);

    assertThat(graph).isNotEqualTo(g2);
  }

  // Node/edge sets and node/edge connections are the same, but directedness differs.

   *         <li>{@code predecessors(node)}: Connecting edge insertion order
   *         <li>{@code successors(node)}: Connecting edge insertion order
   *         <li>{@code incidentEdges(node)}: Stable order
   *         <li>{@code inEdges(node)}: Edge insertion order
   *         <li>{@code outEdges(node)}: Edge insertion order
   *         <li>{@code adjacentEdges(edge)}: Stable order

   *         <li>{@code predecessors(node)}: Connecting edge insertion order
   *         <li>{@code successors(node)}: Connecting edge insertion order
   *         <li>{@code incidentEdges(node)}: Stable order
   *         <li>{@code inEdges(node)}: Edge insertion order
   *         <li>{@code outEdges(node)}: Edge insertion order
   *         <li>{@code adjacentEdges(edge)}: Stable order

  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addEdge(N1, N2, E13);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test

  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addEdge(N1, N2, E13);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test

/**
 * An immutable pair representing the two endpoints of an edge in a graph. The {@link EndpointPair}
 * of a directed edge is an ordered pair of nodes ({@link #source()} and {@link #target()}). The
 * {@link EndpointPair} of an undirected edge is an unordered pair of nodes ({@link #nodeU()} and
 * {@link #nodeV()}).
 *
 * <p>The edge is a self-loop if, and only if, the two endpoints are equal.
 *
 * @author James Sexton

import javax.annotation.CheckForNull;

/**
 * A class to represent the set of edges connecting an (implicit) origin node to a target node.
 *
 * <p>The {@link #nodeToOutEdge} map means this class only works on networks without parallel edges.
 * See {@link MultiEdgesConnecting} for a class that works with parallel edges.
 *
 * @author James Sexton
 * @param <E> Edge parameter type
 */
@ElementTypesAreNonnullByDefault

      // Number of edges remaining is unknown (node's incident edges have been removed).
      AbstractNetworkTest.validateNetwork(network);

      for (int i = numNodesToRemove; i < NUM_NODES; ++i) {
        assertThat(network.removeNode(nodeList.get(i))).isTrue();
      }

      assertThat(network.nodes()).isEmpty();
      assertThat(network.edges()).isEmpty(); // no edges can remain if there's no nodes

      mutableValueGraph.addNode(node);
      return this;
    }

    /**
     * Adds an edge connecting {@code nodeU} to {@code nodeV} if one is not already present, and
     * sets a value for that edge to {@code value} (overwriting the existing value, if any).
     *
     * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be
     * undirected.
     *

    public Builder<N> addNode(N node) {
      mutableGraph.addNode(node);
      return this;
    }

    /**
     * Adds an edge connecting {@code nodeU} to {@code nodeV} if one is not already present.
     *
     * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be
     * undirected.
     *