Add LangGraph adapter execution test

tests/test_langgraph_runtime_adapter.py

@@ -4,7 +4,10 @@ import importlib.util
 
 import pytest
 
+from graph.models import ExecutionGraphDefinition, ExecutionGraphVersion, ExecutionGraphVersionStatus, GraphRun, GraphRunStatus
 from graph.langgraph_runtime import LangGraphRuntime
+from graph.registry import NodeHandlerRegistry, NodeResult
+from graph.spec import ExecutionGraphSpec, GraphEdgeSpec, GraphNodeSpec
 
 
 def test_langgraph_runtime_reports_missing_dependency() -> None:
@@ -15,3 +18,38 @@ def test_langgraph_runtime_reports_missing_dependency() -> None:
 
     with pytest.raises(RuntimeError, match="langgraph package|NodeHandlerRegistry"):
         runtime.run_until_terminal_or_paused(None)  # type: ignore[arg-type]
+
+
+class LangGraphFixtureNode:
+    node_type = "langgraph_fixture"
+    idempotent = True
+    replay_safe = True
+    destructive = False
+
+    def run(self, context: object) -> NodeResult:
+        return NodeResult("COMPLETE", "success", {"executed": True}, {"model_requests": 0})
+
+
+def test_langgraph_runtime_executes_artifex_graph_when_installed() -> None:
+    if importlib.util.find_spec("langgraph") is None:
+        pytest.skip("langgraph is not installed")
+    spec = ExecutionGraphSpec(
+        name="langgraph_fixture",
+        version=1,
+        graph_type="FIXTURE",
+        entry="step",
+        nodes={"step": GraphNodeSpec("step", "langgraph_fixture"), "done": GraphNodeSpec("done", "terminal")},
+        edges=[GraphEdgeSpec("step", "done", "success")],
+        terminal_nodes=["done"],
+    )
+    definition = ExecutionGraphDefinition.objects.create(name=spec.name, graph_type=spec.graph_type)
+    version = ExecutionGraphVersion.objects.create(graph=definition, version=1, status=ExecutionGraphVersionStatus.CHAMPION, graph_spec=spec.to_dict())
+    graph_run = GraphRun.objects.create(execution_graph_version=version, current_node=spec.entry)
+    registry = NodeHandlerRegistry()
+    registry.register(LangGraphFixtureNode())
+
+    result = LangGraphRuntime(registry).run_until_terminal_or_paused(graph_run)
+
+    assert result.status == GraphRunStatus.COMPLETE
+    assert result.current_node == "done"
+    assert result.node_runs.get(node_id="step").output_metadata["executed"] is True