ArrayList<Object> edgeList = new ArrayList<>(network.edges());

      assertThat(network.nodes()).hasSize(NUM_NODES);
      assertThat(network.edges()).hasSize(NUM_EDGES);
      AbstractNetworkTest.validateNetwork(network);

      Collections.shuffle(edgeList, gen);
      int numEdgesToRemove = gen.nextInt(NUM_EDGES);
      for (int i = 0; i < numEdgesToRemove; ++i) {
        Object edge = edgeList.get(i);

      ArrayList<Object> edgeList = new ArrayList<>(network.edges());

      assertThat(network.nodes()).hasSize(NUM_NODES);
      assertThat(network.edges()).hasSize(NUM_EDGES);
      AbstractNetworkTest.validateNetwork(network);

      Collections.shuffle(edgeList, gen);
      int numEdgesToRemove = gen.nextInt(NUM_EDGES);
      for (int i = 0; i < numEdgesToRemove; ++i) {
        Object edge = edgeList.get(i);

 *       locks---to each of the acquired locks, an edge from the soon-to-be-acquired lock is either
 *       verified or created.
 *   <li>If a new edge needs to be created, the outgoing edges of the acquired locks are traversed
 *       to check for a cycle that reaches the lock to be acquired. If no cycle is detected, a new
 *       "safe" edge is created.
 *   <li>If a cycle is detected, an "unsafe" (cyclic) edge is created to represent a potential

 *   <li>graphs whose nodes/edges are insertion-ordered, sorted, or unordered
 *   <li>graphs whose edges have associated values
 * </ul>
 *
 * <p>{@code ValueGraph}, as a subtype of {@code Graph}, explicitly does not support parallel edges,
 * and forbids implementations or extensions with parallel edges. If you need parallel edges, use
 * {@link Network}. (You can use a positive {@code Integer} edge value as a loose representation of

   * treated as if collapsed into a single edge. For example, the {@link #degree(Object)} of a node
   * in the {@link Graph} view may be less than the degree of the same node in this {@link Network}.
   */
  Graph<N> asGraph();

  //
  // Network properties
  //

  /**
   * Returns true if the edges in this network are directed. Directed edges connect a {@link

  @Override
  Set<N> nodes();

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

  //
  // 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.
   */

  Set<N> nodes();

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

  //
  // 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();

  }

  @Test
  public void edges_oneEdge() {
    addEdge(N1, N2, E12);
    assertThat(network.edges()).containsExactly(E12);
  }

  @Test
  public void edges_noEdges() {
    assertThat(network.edges()).isEmpty();
    // Network with no edges, given disconnected nodes
    addNode(N1);
    addNode(N2);
    assertThat(network.edges()).isEmpty();
  }

  @Test

  }

  @Test
  public void edges_oneEdge() {
    addEdge(N1, N2, E12);
    assertThat(network.edges()).containsExactly(E12);
  }

  @Test
  public void edges_noEdges() {
    assertThat(network.edges()).isEmpty();
    // Network with no edges, given disconnected nodes
    addNode(N1);
    addNode(N2);
    assertThat(network.edges()).isEmpty();
  }

  @Test

          assertThat(graph.hasEdgeConnecting(endpoints.nodeU(), endpoints.nodeV())).isTrue();
        }
      }
    }

    sanityCheckSet(graph.edges());
    assertThat(graph.edges()).doesNotContain(EndpointPair.of(graph, new Object(), new Object()));
    assertThat(graph.edges()).isEqualTo(allEndpointPairs);
  }

  /**
   * Verifies that the {@code Set} returned by {@code nodes} has the expected mutability property