}

  @Test
  public void hasCycle_twoCyclicEdges() {
    for (MutableGraph<Integer> graph : graphsToTest) {
      graph.putEdge(1, 2);
      graph.putEdge(2, 1); // no-op in undirected case
    }
    assertThat(hasCycle(directedGraph)).isTrue();
    assertThat(hasCycle(undirectedGraph)).isFalse();
  }

  @Test
  public void hasCycle_threeAcyclicEdges() {

/**
 * Utility {@link RemovalListener} implementations intended for use in testing.
 *
 * @author mike nonemacher
 */
@GwtCompatible(emulated = true)
class TestingRemovalListeners {

  /** Returns a new no-op {@code RemovalListener}. */
  static <K, V> NullRemovalListener<K, V> nullRemovalListener() {
    return new NullRemovalListener<>();
  }

  /** Type-inferring factory method for creating a {@link QueuingRemovalListener}. */

      for (int i = 0; i < iterations; i++) {
        int keyIndex = random.nextInt(nKeys);
        String key = keys.get(keyIndex);
        Operation op = operations[random.nextInt(operations.length)];
        switch (op) {
          case ADD:
            {
              int delta = random.nextInt(10);
              multiset.add(key, delta);
              deltas[keyIndex] += delta;

  }

  @Test
  public void hasCycle_twoCyclicEdges() {
    for (MutableGraph<Integer> graph : graphsToTest) {
      graph.putEdge(1, 2);
      graph.putEdge(2, 1); // no-op in undirected case
    }
    assertThat(hasCycle(directedGraph)).isTrue();
    assertThat(hasCycle(undirectedGraph)).isFalse();
  }

  @Test
  public void hasCycle_threeAcyclicEdges() {

/**
 * Methods factored out so that they can be emulated differently in GWT.
 *
 * @author Chris Povirk
 */
final class Platform {
  /** Serializes and deserializes the specified object (a no-op under GWT). */
  @SuppressWarnings("unchecked")
  static <T> T reserialize(T object) {
    return checkNotNull(object);
  }

  private Platform() {}

 *
 * @author Hayward Chan
 */
@GwtCompatible
final class Platform {
  static <T> T[] clone(T[] array) {
    return array.clone();
  }

  // Class.cast is not supported in GWT.  This method is a no-op in GWT.
  static void checkCast(Class<?> clazz, Object obj) {
    Object unused = clazz.cast(obj);
  }

  static String format(String template, Object... args) {
    return String.format(Locale.ROOT, template, args);

      // since the operation would be a no-op, the exception is not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_VALUE_QUERIES)
  public void testRemove_nullValueQueriesUnsupported() {
    try {
      assertFalse(getMap().remove(k3(), null));
    } catch (NullPointerException tolerated) {
      // since the operation would be a no-op, the exception is not required
    }

      // since the operation would be a no-op, the exception is not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_VALUE_QUERIES)
  public void testRemove_nullValueQueriesUnsupported() {
    try {
      assertFalse(getMap().remove(k3(), null));
    } catch (NullPointerException tolerated) {
      // since the operation would be a no-op, the exception is not required
    }

      // the operation would be a no-op, so exceptions are allowed but not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testReplaceEntry_unsupportedAbsentKey() {
    try {
      getMap().replace(k3(), v3(), v4());
    } catch (UnsupportedOperationException tolerated) {
      // the operation would be a no-op, so exceptions are allowed but not required
    }

      // since the operation would be a no-op, the exception is not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_VALUE_QUERIES)
  public void testRemove_nullValueQueriesUnsupported() {
    try {
      assertFalse(getMap().remove(k3(), null));
    } catch (NullPointerException tolerated) {
      // since the operation would be a no-op, the exception is not required
    }