@Override
    public void to(final String topic) {
        to(topic, Produced.with(keySerde, valueSerde, null));
    }
@Test
    public void shouldNotAllowNullTopicOnToWithProduced() {
        final NullPointerException exception = assertThrows(
            NullPointerException.class,
            () -> testStream.to((String) null, Produced.as("to")));
        assertThat(exception.getMessage(), equalTo("topic can't be null"));
    }