@Test
public void testGetAttributeColumnsEmpty() {

    GraphStore store = new GraphStore();
    NodeImpl node = new NodeImpl("0", store);
    Iterable<Column> pk = node.getAttributeColumns();
    Assert.assertNotNull(pk);
    Iterator<Column> itr = pk.iterator();
    Assert.assertNotNull(itr);
    int size = 0;
    for (; itr.hasNext();) {
        Column c = itr.next();
        Assert.assertTrue(c.isProperty());
        size++;
    }
    Assert.assertTrue(size == getElementPropertiesLength());
}