@Override
    @Deprecated
    public <KR, VR> KStream<KR, VR> transform(final org.apache.kafka.streams.kstream.TransformerSupplier<? super K, ? super V, KeyValue<KR, VR>> transformerSupplier,
                                              final String... stateStoreNames) {
        Objects.requireNonNull(transformerSupplier, "transformerSupplier can't be null");
        final String name = builder.newProcessorName(TRANSFORM_NAME);
        return flatTransform(new TransformerSupplierAdapter<>(transformerSupplier), Named.as(name), stateStoreNames);
    }
@Test
    @SuppressWarnings("deprecation")
    public void shouldNotAllowNullTransformerSupplierOnTransform() {
        final NullPointerException exception = assertThrows(
            NullPointerException.class,
            () -> testStream.transform(null));
        assertThat(exception.getMessage(), equalTo("transformerSupplier can't be null"));
    }