@Test
public void testEmptySiteLinkFilterForItem() {

	SiteLink s1 = Datamodel.makeSiteLink("Title 1", "site1", Collections.emptyList());
	SiteLink s2 = Datamodel.makeSiteLink("Title 2", "site2", Collections.emptyList());
	SiteLink s3 = Datamodel.makeSiteLink("Title 3", "site3", Collections.emptyList());
	SiteLink s4 = Datamodel.makeSiteLink("Title 4", "site4", Collections.emptyList());
	DocumentDataFilter documentDataFilter = new DocumentDataFilter();
	documentDataFilter.setSiteLinkFilter(Collections.emptySet());
	DatamodelFilter filter = new DatamodelFilter(new DataObjectFactoryImpl(), documentDataFilter);
	Map<String, SiteLink> siteLinks = new HashMap<>();
	siteLinks.put(s1.getSiteKey(), s1);
	siteLinks.put(s2.getSiteKey(), s2);
	siteLinks.put(s3.getSiteKey(), s3);
	siteLinks.put(s4.getSiteKey(), s4);
	ItemDocument itemDocument = Datamodel.makeItemDocument(
			Datamodel.makeWikidataItemIdValue("Q42"),
			Collections.emptyList(),
			Collections.emptyList(),
			Collections.emptyList(),
			Collections.emptyList(),
			siteLinks
	);
	ItemDocument itemDocumentFiltered = Datamodel.makeItemDocument(Datamodel.makeWikidataItemIdValue("Q42"),
			Collections.emptyList(), Collections.emptyList(), Collections.emptyList(),
			Collections.emptyList(), Collections.emptyMap()
	);
	assertEquals(itemDocumentFiltered, filter.filter(itemDocument));
}