def METHOD_NAME(self) -> None:
    """Test if adding an edge to empty graph fails as expected."""
    source_id = _get_random_string()
    target_id = _get_random_string()
    graph = Graph()
    result = graph.add_edge(source_id=source_id, target_id=target_id)
    self.assertEqual(False, result)
    self.assertEqual([], graph.edges)