🚨 test(conftest.py): add basic_graph_data fixture to load basic example data

🚨 test(test_websocket.py): add tests for build init, stream, and websocket endpoint
The `basic_graph_data` fixture is added to load the basic example data. The `test_init_build`, `test_stream_build`, and `test_websocket_endpoint` tests are added to test the build init, stream, and websocket endpoint. The `test_websocket_endpoint_after_build` test is added to test the websocket endpoint after the build.

tests/conftest.py

@@ -63,6 +63,12 @@ def get_graph(_type="basic"):
     return Graph(nodes, edges)
 
 
+@pytest.fixture
+def basic_graph_data():
+    with open(pytest.BASIC_EXAMPLE_PATH, "r") as f:
+        return json.load(f)
+
+
 @pytest.fixture
 def basic_graph():
     return get_graph()