### Question:
KafkaTrackingToken implements TrackingToken, Serializable { @Override public String toString() { return "KafkaTrackingToken{" + "positions=" + positions + '}'; } private  KafkaTrackingToken(Map<TopicPartition, Long> positions); @JsonCreator static KafkaTrackingToken newInstance(@JsonProperty("positions") Map<TopicPartition, Long> positions); static KafkaTrackingToken emptyToken(); static boolean isNotEmpty(KafkaTrackingToken token); static boolean isEmpty(KafkaTrackingToken token); @SuppressWarnings("ConstantConditions") static KafkaTrackingToken from(TrackingToken trackingToken); Map<TopicPartition, Long> positions(); KafkaTrackingToken advancedTo(String topic, int partition, long offset); @Override TrackingToken lowerBound(TrackingToken other); @Override TrackingToken upperBound(TrackingToken other); @Override boolean covers(TrackingToken other); @Override boolean equals(Object o); @Override int hashCode(); @Override String toString();  }### Answer:
@Test void testTokenIsHumanReadable() { assertEquals("KafkaTrackingToken{positions={topic-0=0}}", nonEmptyToken().toString()); }