@Test
public void toJsonReturnsExpected() {

    final SubjectsModified underTest =
            SubjectsModified.of(TestConstants.Policy.POLICY_ID, TestConstants.Policy.LABEL,
                    TestConstants.Policy.SUBJECTS, TestConstants.Policy.REVISION_NUMBER, TestConstants.TIMESTAMP,
                    TestConstants.EMPTY_DITTO_HEADERS);
    final JsonObject actualJson = underTest.toJson(FieldType.regularOrSpecial());
    assertThat(actualJson).isEqualTo(KNOWN_JSON);
}