refactor: separate initialization of nodes and edges in test_graph.py (#2828)

* refactor: move test_graph.py

* refactor: allow Graph to be initialized with no nodes and edges

The Graph class in `base.py` was refactored to separate the initialization of nodes and edges into a separate method called `add_nodes_and_edges()`. This improves code readability and maintainability by organizing the code logic more effectively.

* refactor: separate initialization of nodes and edges in get_graph()

The `get_graph()` function in `conftest.py` was refactored to separate the initialization of nodes and edges. This improves code readability and maintainability by organizing the code logic more effectively.

* refactor: separate initialization of nodes and edges in test_graph.py

* refactor: separate initialization of nodes and edges in base.py

The `add_node()` and `add_edge()` methods were added to the `Graph` class in `base.py` to separate the initialization of nodes and edges. This improves code readability and maintainability by organizing the code logic more effectively.

src/backend/tests/conftest.py

@@ -158,7 +158,9 @@ def get_graph(_type="basic"):
     data_graph = flow_graph["data"]
     nodes = data_graph["nodes"]
     edges = data_graph["edges"]
-    return Graph(nodes, edges)
+    graph = Graph()
+    graph.add_nodes_and_edges(nodes, edges)
+    return graph
 
 
 @pytest.fixture

src/backend/tests/unit/graph/test_graph.py

@@ -116,7 +116,8 @@ def test_invalid_node_types():
         "edges": [],
     }
     with pytest.raises(Exception):
-        Graph(graph_data["nodes"], graph_data["edges"])
+        g = Graph()
+        g.add_nodes_and_edges(graph_data["nodes"], graph_data["edges"])
 
 
 def test_get_vertices_with_target(basic_graph):