test(reports): cover SlackResponse.data scope path and backoff recovery

Close two gaps in the Slack v1-deprecation tests surfaced in review:

- should_use_v2_api scope detection was only exercised with a plain-dict
  response; the production-default path reads the error code via
  getattr(response, "data") on a real SlackResponse. Add a case using the
  existing MockResponse helper so that branch is covered.
- The backoff switch to NotificationUnprocessableException is meant to let a
  transient failure retry and ultimately succeed; only persistent-fail (5x)
  and never-retry were tested. Add a fail-twice-then-succeed case asserting
  3 attempts and the success gauge.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/unit_tests/reports/notifications/slack_tests.py

@@ -756,6 +756,42 @@ def test_v2_send_retries_on_transient_slack_api_error(
     assert slack_client_mock.return_value.chat_postMessage.call_count == 5
 
 
+@patch("superset.reports.notifications.slackv2.g")
+@patch("superset.reports.notifications.slackv2.get_slack_client")
+def test_v2_send_retries_then_succeeds_on_transient_failure(
+    slack_client_mock: MagicMock,
+    flask_global_mock: MagicMock,
+    mock_header_data,
+) -> None:
+    """The point of switching backoff to NotificationUnprocessableException is
+    that a *transient* failure now retries and the send ultimately succeeds —
+    behavior the old (dead) SlackApiError decorator never delivered. Fail twice,
+    then succeed: send() must return normally after exactly 3 attempts and still
+    record the success gauge.
+    """
+    flask_global_mock.logs_context = {}
+    slack_client_mock.return_value.chat_postMessage.side_effect = [
+        SlackApiError(
+            message="rate limited", response={"ok": False, "error": "ratelimited"}
+        ),
+        SlackApiError(
+            message="rate limited", response={"ok": False, "error": "ratelimited"}
+        ),
+        {"ok": True},
+    ]
+
+    content = _make_content(mock_header_data)
+    notification = _make_v2_notification(content, target="C12345")
+
+    with patch(
+        "superset.extensions.stats_logger_manager.instance.gauge"
+    ) as statsd_mock:
+        notification.send()
+
+    assert slack_client_mock.return_value.chat_postMessage.call_count == 3
+    statsd_mock.assert_called_with("reports.slack.send.ok", 1)
+
+
 @patch("superset.reports.notifications.slackv2.g")
 @patch("superset.reports.notifications.slackv2.get_slack_client")
 def test_v2_send_does_not_retry_param_errors(

tests/unit_tests/utils/slack_test.py

@@ -325,6 +325,38 @@ class TestShouldUseV2Api:
             assert "channels:read" in c.args[0]
             assert "groups:read" in c.args[0]
 
+    def test_scope_missing_detected_via_slack_response_data_shape(self, mocker):
+        """The real Slack SDK sets `SlackApiError.response` to a `SlackResponse`
+        whose payload lives in `.data` — not a plain dict. This is the
+        production-default code path, so it must be exercised directly:
+        `should_use_v2_api` reads the error code via `getattr(response, "data")`
+        and the scope-missing branch must still fire.
+        """
+        mocker.patch(
+            "superset.utils.slack.feature_flag_manager.is_feature_enabled",
+            return_value=True,
+        )
+        mock_client = mocker.Mock()
+        # MockResponse mirrors SlackResponse: the error payload is on `.data`,
+        # exactly as the live SDK delivers it.
+        mock_client.conversations_list.side_effect = SlackApiError(
+            message="missing_scope",
+            response=MockResponse({"ok": False, "error": "missing_scope"}),
+        )
+        mocker.patch("superset.utils.slack.get_slack_client", return_value=mock_client)
+        logger_mock = mocker.patch("superset.utils.slack.logger")
+
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            assert should_use_v2_api() is False
+
+        deprecation_warnings = [
+            w for w in caught if issubclass(w.category, DeprecationWarning)
+        ]
+        assert len(deprecation_warnings) == 1
+        assert logger_mock.warning.call_count == 1
+        assert "channels:read" in logger_mock.warning.call_args.args[0]
+
     @pytest.mark.parametrize(
         "error_code",
         ["invalid_auth", "ratelimited", "fatal_error", "account_inactive", ""],