@Override
    public KTable<K, V> reduce(final Reducer<V> adder,
                               final Reducer<V> subtractor,
                               final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized) {
        return reduce(adder, subtractor, NamedInternal.empty(), materialized);
    }
@Test
    public void shouldNotAllowNullAdderOnReduce() {
        assertThrows(NullPointerException.class, () -> groupedTable.reduce(
            null,
            MockReducer.STRING_REMOVER,
            Materialized.as("store")));
    }