### Question:
DirectoryRosterStore implements RosterStore { public static DirectoryRosterStore open(final File baseDir) { DirectoryRosterStore store = new DirectoryRosterStore(baseDir); String s = FileUtils.readFile(store.getVersionFile()); if (s != null && s.startsWith(STORE_ID + "\n")) { return store; } else { return null; } } private  DirectoryRosterStore(final File baseDir); static DirectoryRosterStore init(final File baseDir); static DirectoryRosterStore open(final File baseDir); @Override List<Item> getEntries(); @Override Item getEntry(Jid bareJid); @Override String getRosterVersion(); @Override boolean addEntry(Item item, String version); @Override boolean removeEntry(Jid bareJid, String version); @Override boolean resetEntries(Collection<Item> items, String version); @Override void resetStore();  }### Answer:
@Test public void testStoreUninitialized() throws IOException { File storeDir = tmpFolder.newFolder(); assertNull(DirectoryRosterStore.open(storeDir)); }