### Question:
StartupDateMetadataContributor implements MetadataContributor { @Override public Map<String, String> getMetadata() { return singletonMap("startup", this.timestamp.format(DateTimeFormatter.ISO_DATE_TIME)); }  @Override Map<String, String> getMetadata();  }### Answer:
@Test public void should_return_startupdate() { StartupDateMetadataContributor contributor = new StartupDateMetadataContributor(); Map<String, String> metadata = contributor.getMetadata(); assertThat(metadata).hasSize(1).hasEntrySatisfying("startup", (value) -> assertThat(value).isNotEmpty()); }