Create Stackchain Lab agent collaboration loop

tests/test_lab_loop.py

@@ -0,0 +1,38 @@
+import unittest
+
+from scripts.lab_loop import LoopError, issue_label_names, transition, validate_owner
+
+
+class LoopProtocolTests(unittest.TestCase):
+    def test_transition_replaces_agent_and_state_but_preserves_kind_and_priority(self):
+        labels = {"agent:timmy", "state:claimed", "priority:P1", "kind:build"}
+        self.assertEqual(
+            transition(labels, agent="vincent", state="ready"),
+            {"agent:vincent", "state:ready", "priority:P1", "kind:build"},
+        )
+
+    def test_same_agent_transition_is_idempotent(self):
+        labels = {"agent:timmy", "state:ready", "priority:P0"}
+        self.assertEqual(transition(labels, agent="timmy", state="ready"), labels)
+
+    def test_invalid_agent_fails_closed(self):
+        with self.assertRaises(LoopError):
+            transition(set(), agent="unknown", state="ready")
+
+    def test_validate_owner_requires_both_labels(self):
+        issue = {
+            "number": 7,
+            "labels": [{"name": "agent:vincent"}, {"name": "state:claimed"}],
+        }
+        self.assertEqual(validate_owner(issue, "vincent", "claimed"), {"agent:vincent", "state:claimed"})
+        with self.assertRaises(LoopError):
+            validate_owner(issue, "timmy", "claimed")
+        with self.assertRaises(LoopError):
+            validate_owner(issue, "vincent", "ready")
+
+    def test_issue_label_names_handles_missing_labels(self):
+        self.assertEqual(issue_label_names({}), set())
+
+
+if __name__ == "__main__":
+    unittest.main()