public void setRecordMetadata(final String topic,
                                  final int partition,
                                  final long offset) {
        recordMetadata = new MockRecordMetadata(topic, partition, offset);
    }
The context exposes these metadata for use in the processor. Normally, they are set by the Kafka Streams framework,
but for the purpose of driving unit tests, you can set them directly.

@param topic     A topic name
@param partition A partition number
@param offset    A record offset
streams/test-utils/src/main/java/org/apache/kafka/streams/processor/api/MockProcessorContext.java