verify(P4): migrate-ssm-except-narrowing — 4-layer verify PASS + ship

VERIFY: structural — narrowed excepts; behavioral — 48 tests + CI PASS; security — non-ParameterNotFound errors surface; quality — 2 new + 2 updated tests.

---ci---
project: acdl
phase: 4
milestone: v1.16
status: complete
phase_role: execution
requirements:
  covered: [REQ-168]
  partial: []
---/ci---

tests/test_migrate_ssm_paths.py

@@ -74,4 +74,52 @@ class TestMapPath:
 
     def test_preserves_value_segment_exactly(self):
         # Hyphens, dots, underscores in output names are preserved
-        assert map_path("/acdl/dev/c-1/my.output-name_2") == "/nova/dev/c-1/my.output-name_2"
+        assert map_path("/acdl/dev/c-1/my.output-name_2") == "/nova/dev/c-1/my.output-name_2"
+
+class TestNarrowedException:
+    """P4 (REQ-168): the copy_one_param except is narrowed to
+    ParameterNotFound; non-ParameterNotFound errors surface (not swallowed)."""
+
+    def test_parameter_not_found_proceeds_to_put(self):
+        """A ParameterNotFound on the dest get_parameter (target absent) is
+        the expected 'proceed to put' path — not an error."""
+        from unittest import mock
+        import migrate_ssm_paths as m
+
+        class FakeExceptions:
+            ParameterNotFound = type("ParameterNotFound", (Exception,), {})
+
+        fake_client = mock.Mock()
+        fake_client.exceptions = FakeExceptions
+        # source get_parameter succeeds; dest get_parameter raises ParameterNotFound
+        fake_client.get_parameter.side_effect = [
+            {"Parameter": {"Value": "v", "Type": "String", "KeyId": None}},
+            FakeExceptions.ParameterNotFound(),
+        ]
+        fake_client.put_parameter.return_value = {"Version": 1}
+        result = m.copy_one_param(fake_client, "/acdl/dev/c/out", "/nova/dev/c/out")
+        assert result == "copied"
+        fake_client.put_parameter.assert_called_once()
+
+    def test_non_parameter_not_found_error_is_raised(self):
+        """A non-ParameterNotFound AWS error (e.g. ThrottlingException) on
+        the dest get_parameter is raised, not swallowed (P4, REQ-168)."""
+        from unittest import mock
+        import migrate_ssm_paths as m
+
+        class FakeExceptions:
+            ParameterNotFound = type("ParameterNotFound", (Exception,), {})
+
+        class ThrottlingException(Exception):
+            pass
+
+        fake_client = mock.Mock()
+        fake_client.exceptions = FakeExceptions
+        # source get_parameter succeeds; dest get_parameter raises Throttling
+        fake_client.get_parameter.side_effect = [
+            {"Parameter": {"Value": "v", "Type": "String", "KeyId": None}},
+            ThrottlingException("slow down"),
+        ]
+        with pytest.raises(ThrottlingException):
+            m.copy_one_param(fake_client, "/acdl/dev/c/out", "/nova/dev/c/out")
+        fake_client.put_parameter.assert_not_called()

tests/test_output_publisher.py

@@ -134,7 +134,11 @@ class TestPublishToSsm:
             def flaky_put(**kwargs):
                 call_count["n"] += 1
                 if "bad" in kwargs["Name"]:
-                    raise Exception("simulated failure")
+                    from botocore.exceptions import ClientError
+                    raise ClientError(
+                        {"Error": {"Code": "InternalError", "Message": "simulated"}},
+                        "PutParameter",
+                    )
                 return real_put(**kwargs)
 
             with mock.patch("core.output_publisher._ssm_client", return_value=ssm):
@@ -272,10 +276,11 @@ class TestPostGithubComment:
         assert "/issues/5/comments" in captured["url"]
 
     def test_returns_false_on_exception(self, monkeypatch):
+        import urllib.error
         monkeypatch.setenv("GITHUB_TOKEN", "tok")
         monkeypatch.setenv("GITHUB_REPOSITORY", "acdl/acdl")
         monkeypatch.setenv("GITHUB_REF", "refs/pull/1/merge")
-        with mock.patch("urllib.request.urlopen", side_effect=Exception("boom")):
+        with mock.patch("urllib.request.urlopen", side_effect=urllib.error.URLError("boom")):
             assert post_github_comment("body") is False
 
     def test_uses_gh_token_fallback(self, monkeypatch):