### Question:
ConnectionManager { public static ConnectionGroup getOrCreateConnectionGroup(String namespace) { AssertUtil.assertNotBlank(namespace, "namespace should not be empty"); ConnectionGroup group = getOrCreateGroup(namespace); return group; } private  ConnectionManager(); static int getConnectedCount(String namespace); static ConnectionGroup getOrCreateGroup(String namespace); static void removeConnection(String address); static void removeConnection(String namespace, String address); static ConnectionGroup addConnection(String namespace, String address); static ConnectionGroup getOrCreateConnectionGroup(String namespace); static ConnectionGroup getConnectionGroup(String namespace);  }### Answer:
@Test public void testGetOrCreateConnectionGroup() { String namespace = "test-namespace"; assertNull(ConnectionManager.getConnectionGroup(namespace)); ConnectionGroup group1 = ConnectionManager.getOrCreateConnectionGroup(namespace); assertNotNull(group1); ConnectionManager.addConnection(namespace, "12.23.34.45:1997"); ConnectionGroup group2 = ConnectionManager.getOrCreateConnectionGroup(namespace); assertSame(group1, group2); }