@Test(expected = UnsupportedOperationException.class)
public void getMarkersReturnsUnmodifiableSet() {

    final JsonValueFieldDefinition<JsonValue> underTest =
            JsonValueFieldDefinition.newInstance(KNOWN_JSON_POINTER, JsonValue.class, JsonValue::isObject,
                    JsonValue::asObject, knownFieldMarkers);
    final Set<JsonFieldMarker> markers = underTest.getMarkers();
    markers.add(mock(JsonFieldMarker.class));
}