@Override
    public Set<K> keySet() {
        Set<K> keys = Sets.newHashSet();
        items.keySet().forEach(k -> keys.add(serializer.decode(k)));
        return keys;
    }
@Test
    public void testKeySet() throws Exception {
        //Tests key set generation
        fillMap(10);
        Set<Integer> keys = map.keySet();
        for (int i = 0; i < 10; i++) {
            assertTrue("The key set doesn't contain all keys 0-9", keys.contains(i));
        }
        assertEquals("The key set has an incorrect number of entries", 10, keys.size());
    }