Update tests/unit/agent_factory/test_graph_builder.py

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

tests/unit/agent_factory/test_graph_builder.py

@@ -266,7 +266,7 @@ class TestResearchGraph:
         graph.add_node(unreachable)
         graph.add_edge(SequentialEdge(from_node="start", to_node="end"))
 
-        errors = graph.validate()
+        errors = graph.validate_structure()
         assert len(errors) > 0
         assert any("unreachable" in error.lower() for error in errors)