Add lightweight unittest coverage for stability fixes

tests/test_runtime_state.py

@@ -0,0 +1,28 @@
+import json
+import tempfile
+import unittest
+from pathlib import Path
+
+from services import runtime_state
+
+
+class RuntimeStateTests(unittest.TestCase):
+    def test_set_and_get_persist_between_loads(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            path = Path(tmp) / "runtime.json"
+            runtime_state.configure(str(path))
+
+            runtime_state.set_state("foo", {"bar": 1})
+            self.assertEqual(runtime_state.get("foo"), {"bar": 1})
+
+            # Force a fresh in-memory state and load from disk again.
+            runtime_state._STATE = {}  # type: ignore[attr-defined]
+            runtime_state._LOADED = False  # type: ignore[attr-defined]
+            self.assertEqual(runtime_state.get("foo"), {"bar": 1})
+
+            raw = json.loads(path.read_text(encoding="utf-8"))
+            self.assertEqual(raw.get("foo"), {"bar": 1})
+
+
+if __name__ == "__main__":
+    unittest.main()