@Override
    public <VO, VR> KStream<K, VR> outerJoin(final KStream<K, VO> otherStream,
                                             final ValueJoiner<? super V, ? super VO, ? extends VR> joiner,
                                             final JoinWindows windows) {
        return outerJoin(otherStream, toValueJoinerWithKey(joiner), windows);
    }
@SuppressWarnings("deprecation")
    @Test
    public void shouldNotAllowNullOtherStreamOnOuterJoin() {
        final NullPointerException exception = assertThrows(
            NullPointerException.class,
            () -> testStream.outerJoin(null, MockValueJoiner.TOSTRING_JOINER, JoinWindows.of(ofMillis(10))));
        assertThat(exception.getMessage(), equalTo("otherStream can't be null"));
    }