return org;
    }

    private BuildStep merge(BuildStep node1, BuildStep node2) {
        node1.predecessors.addAll(node2.predecessors);
        node1.successors.addAll(node2.successors);
        node2.mojos.forEach((k, v) -> node1.mojos.merge(k, v, this::mergeMojos));
        return node1;
    }

    assume().that(graphIsMutable()).isTrue();

    addNode(N1);
    Set<Integer> successors = graph.successors(N1);
    assertThrows(UnsupportedOperationException.class, () -> successors.add(N2));
    putEdge(N1, N2);
    assertThat(graph.successors(N1)).containsExactlyElementsIn(successors);
  }

  @Override
  @Test
  public void incidentEdges_checkReturnedSetMutability() {

      }

      @Override
      public Set<N> predecessors(N node) {
        return AbstractNetwork.this.predecessors(node);
      }

      @Override
      public Set<N> successors(N node) {
        return AbstractNetwork.this.successors(node);
      }

      // DO NOT override the AbstractGraph *degree() implementations.
    };
  }

  @Override
  public int degree(N node) {
    if (isDirected()) {

 * which has a method {@code getChildren()} that retrieves its successors in a graph:
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, MyNode::getChildren);
 * }
 *
 * <p>If you have some other mechanism for returning the successors of a node, or one that doesn't
 * return an {@code Iterable<? extends N>}, then you can use a lambda to perform a more general

import java.io.Serializable;
import java.util.Map;
import java.util.Set;

import org.dbflute.Entity;
import org.dbflute.FunCustodial;
import org.dbflute.dbmeta.accessory.EntityModifiedProperties;
import org.dbflute.dbmeta.accessory.EntityUniqueDrivenProperties;
import org.dbflute.util.DfCollectionUtil;
import org.opensearch.action.delete.DeleteRequestBuilder;
import org.opensearch.action.index.IndexRequestBuilder;

/**

import java.io.Serializable;
import java.util.Map;
import java.util.Set;

import org.dbflute.Entity;
import org.dbflute.FunCustodial;
import org.dbflute.dbmeta.accessory.EntityModifiedProperties;
import org.dbflute.dbmeta.accessory.EntityUniqueDrivenProperties;
import org.dbflute.util.DfCollectionUtil;
import org.opensearch.action.delete.DeleteRequestBuilder;
import org.opensearch.action.index.IndexRequestBuilder;

/**

 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 */
interface GraphConnections<N, V> {

  Set<N> adjacentNodes();

  Set<N> predecessors();

  Set<N> successors();

  /**
   * Returns an iterator over the incident edges.
   *
   * @param thisNode The node that this all of the connections in this class are connected to.
   */

  @Override
  @Test
  public void successors_checkReturnedSetMutability() {
    addNode(N1);
    Set<Integer> successors = network.successors(N1);
    assertThrows(UnsupportedOperationException.class, () -> successors.add(N2));
    addEdge(N1, N2, E12);
    assertThat(network.successors(N1)).containsExactlyElementsIn(successors);
  }

  @Test
  public void edges_containsOrderMismatch() {
    addEdge(N1, N2, E12);

    return delegate().adjacentNodes(node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return delegate().predecessors(node);
  }

  @Override
  public Set<N> successors(N node) {
    return delegate().successors(node);
  }

  @Override
  public Set<EndpointPair<N>> incidentEdges(N node) {
    return delegate().incidentEdges(node);
  }

  @Override
  public int degree(N node) {

    return delegate().adjacentNodes(node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return delegate().predecessors(node);
  }

  @Override
  public Set<N> successors(N node) {
    return delegate().successors(node);
  }

  @Override
  public Set<E> incidentEdges(N node) {
    return delegate().incidentEdges(node);
  }

  @Override
  public Set<E> inEdges(N node) {