startDay = daysInLastMonth - 6;

            var curDate = moment([lastYear, lastMonth, startDay, 12, minute, second]);

            var col, row;
            for (var i = 0, col = 0, row = 0; i < 42; i++, col++, curDate = moment(curDate).add(24, 'hour')) {
                if (i > 0 && col % 7 === 0) {
                    col = 0;
                    row++;
                }

    assertEquals(2, frequency(list.iterator(), "a"));
    assertEquals(1, frequency(list.iterator(), "b"));
    assertEquals(0, frequency(list.iterator(), "c"));
    assertEquals(0, frequency(list.iterator(), 4.2));
    assertEquals(3, frequency(list.iterator(), null));
  }

  @GwtIncompatible // slow (~4s)
  public void testSingletonIterator() {
    new IteratorTester<Integer>(

    assertEquals(2, frequency(list.iterator(), "a"));
    assertEquals(1, frequency(list.iterator(), "b"));
    assertEquals(0, frequency(list.iterator(), "c"));
    assertEquals(0, frequency(list.iterator(), 4.2));
    assertEquals(3, frequency(list.iterator(), null));
  }

  @GwtIncompatible // slow (~4s)
  public void testSingletonIterator() {
    new IteratorTester<Integer>(