public static String toJson(MetadataUpdate metadataUpdate) {
    return toJson(metadataUpdate, false);
  }
@Test
  public void testAssignUUIDFromJson() {
    String uuid = "9510c070-5e6d-4b40-bf40-a8915bb76e5d";
    String expected =
        "{\"action\":\"assign-uuid\",\"uuid\":\"9510c070-5e6d-4b40-bf40-a8915bb76e5d\"}";
    MetadataUpdate actual = new MetadataUpdate.AssignUUID(uuid);
    assertThat(MetadataUpdateParser.toJson(actual))
        .as("Assign UUID should convert to the correct JSON value")
        .isEqualTo(expected);
  }