@Test
public void testCount() {

    TrackingMultimap<String, Integer> tmmap = (TrackingMultimap<String, Integer>) map;
    tmmap.put("a", Sets.newHashSet(1, 2, 3));
    tmmap.put("b", Sets.newHashSet(1, 2, 3));
    tmmap.put("c", Sets.newHashSet(1, 2, 3, 4));
    AtomicInteger count = new AtomicInteger(0);
    tmmap.forEach((key, values) -> {
        count.addAndGet(values.size());
    });
    Assert.assertEquals(tmmap.count(), count.get());
}