@Override
    public void clear() {
        complete(asyncCounterMap.clear());
    }
@Test
    public void testClear() {
        atomicCounterMap.putIfAbsent(KEY1, VALUE1);
        assertThat(atomicCounterMap.size(), is(1));
        atomicCounterMap.clear();
        assertThat(atomicCounterMap.size(), is(0));
    }