@J2ktIncompatible
  @GwtIncompatible // reflection
  public void testIterables_nullCheck() throws Exception {
    new ClassSanityTester()
        .forAllPublicStaticMethods(Iterables.class)
        .thatReturn(Iterable.class)
        .testNulls();
  }

  private static void verifyMergeSorted(
      Iterable<Iterable<Integer>> iterables, Iterable<Integer> unsortedExpected) {