@GwtIncompatible // SerializableTester
  public void testIsNull_serialization() {
    Predicate<String> pre = Predicates.isNull();
    Predicate<String> post = SerializableTester.reserializeAndAssert(pre);
    assertEquals(pre.apply("foo"), post.apply("foo"));
    assertEquals(pre.apply(null), post.apply(null));
  }

  public void testNotNull_apply() {
    Predicate<@Nullable Integer> notNull = Predicates.notNull();

      if (childItr.hasNext()) {
        stack.addLast(childItr);
      }
      return result;
    }
  }

  /**
   * Returns an unmodifiable iterable over the nodes in a tree structure, using post-order
   * traversal. That is, each node's subtrees are traversed before the node itself is returned.
   *
   * <p>No guarantees are made about the behavior of the traversal when nodes change while iteration

    bus.register(compCatcher);

    // Two additional event types: Object and Comparable<?> (played by Integer)
    Object objEvent = new Object();
    Object compEvent = 6;

    bus.post(EVENT);
    bus.post(objEvent);
    bus.post(compEvent);

    // Check the StringCatcher...
    List<String> stringEvents = stringCatcher.getEvents();
    assertEquals("Only one String should be delivered.", 1, stringEvents.size());

    bus.register(compCatcher);

    // Two additional event types: Object and Comparable<?> (played by Integer)
    Object objEvent = new Object();
    Object compEvent = 6;

    bus.post(EVENT);
    bus.post(objEvent);
    bus.post(compEvent);

    // Check the StringCatcher...
    List<String> stringEvents = stringCatcher.getEvents();
    assertEquals("Only one String should be delivered.", 1, stringEvents.size());

      </plugin>
      <plugin>
        <artifactId>maven-source-plugin</artifactId>
        <executions>
          <execution>
            <id>attach-test-sources</id>
            <phase>post-integration-test</phase>
            <goals><goal>test-jar</goal></goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-jar-plugin</artifactId>

      </plugin>
      <plugin>
        <artifactId>maven-source-plugin</artifactId>
        <executions>
          <execution>
            <id>attach-test-sources</id>
            <phase>post-integration-test</phase>
            <goals><goal>test-jar</goal></goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-surefire-plugin</artifactId>

  @GwtIncompatible // SerializableTester
  public void testIsNull_serialization() {
    Predicate<String> pre = Predicates.isNull();
    Predicate<String> post = SerializableTester.reserializeAndAssert(pre);
    assertEquals(pre.apply("foo"), post.apply("foo"));
    assertEquals(pre.apply(null), post.apply(null));
  }

  public void testNotNull_apply() {
    Predicate<@Nullable Integer> notNull = Predicates.notNull();

      </plugin>
      <plugin>
        <artifactId>maven-source-plugin</artifactId>
        <executions>
          <execution>
            <id>attach-test-sources</id>
            <phase>post-integration-test</phase>
            <goals><goal>test-jar</goal></goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-jar-plugin</artifactId>

      </plugin>
      <plugin>
        <artifactId>maven-source-plugin</artifactId>
        <executions>
          <execution>
            <id>attach-test-sources</id>
            <phase>post-integration-test</phase>
            <goals><goal>test-jar</goal></goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-surefire-plugin</artifactId>

      }
    };
  }

  /**
   * Returns an unmodifiable {@code Iterable} over the nodes reachable from {@code startNode}, in
   * the order of a depth-first post-order traversal. "Post-order" implies that nodes appear in the
   * {@code Iterable} in the order in which they are visited for the last time.
   *