### Question:
SoapTagService extends AbstractService implements TagService { @Override public void addFolderTags(String sid, long folderId, String[] tags) throws Exception { SoapFolderService folderService = getFolderService(); WSFolder folder = folderService.getFolder(sid, folderId); if (folder == null) return; User user = validateSession(sid); checkWriteEnable(user, folderId); for (String tag : tags) folder.addTag(tag); folderService.update(sid, folder); }  @Override void setDocumentTags(String sid, long docId, String[] tags); @Override void addDocumentTags(String sid, long docId, String[] tags); @Override String[] getDocumentTags(String sid, long docId); @Override void setFolderTags(String sid, long folderId, String[] tags); @Override void addFolderTags(String sid, long folderId, String[] tags); @Override String[] getFolderTags(String sid, long folderId); @Override String[] getTags(String sid); @Override String[] getTagsPreset(String sid); @Override WSTagCloud[] getTagCloud(String sid); @Override WSDocument[] findDocumentsByTag(String sid, String tag); @Override WSFolder[] findFoldersByTag(String sid, String tag);  }### Answer:
@Test public void testAddFolderTags() throws Exception { tagService.addFolderTags("", 4L, new String[] { "pippo", "pluto" }); WSFolder[] folders = tagService.findFoldersByTag("", "pippo"); Assert.assertNotNull(folders); Assert.assertEquals(1, folders.length); folders = tagService.findFoldersByTag("", "unexisting"); Assert.assertNotNull(folders); Assert.assertEquals(0, folders.length); }