*
   * @throws IllegalArgumentException if any element in {@code nodes} is not a node in the graph
   */
  public static <N, E> MutableNetwork<N, E> inducedSubgraph(
      Network<N, E> network, Iterable<? extends N> nodes) {
    MutableNetwork<N, E> subgraph =
        (nodes instanceof Collection)
            ? NetworkBuilder.from(network).expectedNodeCount(((Collection) nodes).size()).build()

@AndroidIncompatible
// TODO(cpovirk): Figure out Android JUnit 4 support. Does it work with Gingerbread? @RunWith?
@RunWith(Parameterized.class)
@NullUnmarked
public final class DefaultNetworkImplementationsTest {
  private MutableNetwork<Integer, String> network;
  private NetworkForTest<Integer, String> networkForTest;
  private static final Integer N1 = 1;
  private static final Integer N2 = 2;
  private static final Integer NODE_NOT_IN_GRAPH = 1000;

  public void forTree_acceptsDirectedNetwork() throws Exception {
    MutableNetwork<String, Integer> network = NetworkBuilder.directed().build();
    network.addEdge("a", "b", 11);

    Traverser.forTree(network); // Does not throw
  }

  @Test
  public void forTree_withUndirectedNetwork_throws() throws Exception {
    MutableNetwork<String, Integer> network = NetworkBuilder.undirected().build();

  public void forTree_acceptsDirectedNetwork() throws Exception {
    MutableNetwork<String, Integer> network = NetworkBuilder.directed().build();
    network.addEdge("a", "b", 11);

    Traverser.forTree(network); // Does not throw
  }

  @Test
  public void forTree_withUndirectedNetwork_throws() throws Exception {
    MutableNetwork<String, Integer> network = NetworkBuilder.undirected().build();