private static final int RECURSE_DEPTH = 2;

  public void testCombinationsExhaustively_startingFromNatural() {
    testExhaustively(Ordering.<String>natural(), "a", "b", "d");
  }

  @GwtIncompatible // too slow
  public void testCombinationsExhaustively_startingFromExplicit() {
    testExhaustively(Ordering.explicit("a", "b", "c", "d"), "a", "b", "d");
  }

  @GwtIncompatible // too slow

  private static final int RECURSE_DEPTH = 2;

  public void testCombinationsExhaustively_startingFromNatural() {
    testExhaustively(Ordering.<String>natural(), "a", "b", "d");
  }

  @GwtIncompatible // too slow
  public void testCombinationsExhaustively_startingFromExplicit() {
    testExhaustively(Ordering.explicit("a", "b", "c", "d"), "a", "b", "d");
  }

  @GwtIncompatible // too slow