}

  @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() {

      // 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
    }

  public void testOrdering() {
    final List<Integer> callOrder = Lists.newArrayList();

    class FakeOp implements Runnable {
      final int op;

      FakeOp(int op) {
        this.op = op;
      }

      @Override
      public void run() {
        callOrder.add(op);
      }
    }

    e.execute(new FakeOp(0));
    e.execute(new FakeOp(1));
    e.execute(new FakeOp(2));
    fakePool.runAll();

      // 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
    }

      // permitted not to throw because it would be a no-op
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEY_QUERIES)
  public void testReplace_absentNullKeyUnsupported() {
    try {
      getMap().replace(null, v3());
    } catch (NullPointerException tolerated) {
      // permitted not to throw because it would be a no-op
    }
    expectUnchanged();
  }

      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;

      // 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
    }

 * serialization tests require more setup. This no-op behavior allows test authors to intersperse
 * {@code SerializableTester} calls with other, GWT-compatible tests.
 *
 * @author Mike Bostock
 * @since 10.0
 */
@GwtCompatible // but no-op!
@ElementTypesAreNonnullByDefault
public final class SerializableTester {
  private SerializableTester() {}

  /**