expectedSubgraph.addEdge(N4, N4, E44);

    assertThat(inducedSubgraph(directedGraph, nodeSubset)).isEqualTo(expectedSubgraph);
  }

  @Test
  public void inducedSubgraph_nodeNotInGraph() {
    MutableNetwork<Integer, String> undirectedGraph = NetworkBuilder.undirected().build();

    assertThrows(
        IllegalArgumentException.class,
        () -> inducedSubgraph(undirectedGraph, ImmutableSet.of(N1)));
  }

  @Test

   * from {@code graph} for which both nodes are contained by {@code nodes}.
   *
   * @throws IllegalArgumentException if any element in {@code nodes} is not a node in the graph
   */
  public static <N> MutableGraph<N> inducedSubgraph(Graph<N> graph, Iterable<? extends N> nodes) {
    MutableGraph<N> subgraph =
        (nodes instanceof Collection)
            ? GraphBuilder.from(graph).expectedNodeCount(((Collection) nodes).size()).build()