add tests pipeline manager

- Introduced tests for `listen` and `drain_queue` methods.
- Verified logging of unexpected exceptions during queue processing.
- Ensured specific items and sentinel values are ignored during queue operations.
- Increases test coverage

tests/unit/framework/test_pipeline_manager.py

@@ -3,6 +3,7 @@
 # pylint: disable=attribute-defined-outside-init
 # pylint: disable=unnecessary-lambda-assignment
 import multiprocessing
+import time
 from copy import deepcopy
 from logging import Logger
 from logging.config import dictConfig
@@ -194,6 +195,21 @@ def test_restart_failed_pipelines_sets_old_pipeline_index(self):
             pipeline_manager.restart_failed_pipeline()
             mock_create_pipeline.assert_called_once_with(1)
 
+    def test_restart_failed_pipeline_adds_error_output_health_check_to_metrics_exporter(
+        self, tmp_path
+    ):
+        mock_env = {"PROMETHEUS_MULTIPROC_DIR": str(tmp_path)}
+        with mock.patch.dict("os.environ", mock_env):
+            with mock.patch("logprep.framework.pipeline_manager.OutputQueueListener"):
+                with mock.patch("logprep.framework.pipeline_manager.ThrottlingQueue") as mock_queue:
+                    self.config.metrics = MetricsConfig(enabled=True)
+                    self.config.error_output = {"dummy": {"type": "dummy_output"}}
+                    pipeline_manager = PipelineManager(self.config)
+                    mock_export = mock.MagicMock()
+                    pipeline_manager.prometheus_exporter = mock_export
+                    pipeline_manager.set_count(1)
+                    mock_export.update_healthchecks.assert_called()
+
     def test_pipeline_manager_sets_queue_size_for_http_input(self):
         config = deepcopy(self.config)
         config.input = {
@@ -587,3 +603,80 @@ def test_listen_ensures_error_queue_is_closed_after_drained(self):
         listener._listen()
         with pytest.raises(ValueError, match="is closed"):
             listener.queue.put("test")
+
+    @mock.patch(
+        "logprep.framework.pipeline_manager.OutputQueueListener.get_output_instance",
+    )
+    def test_listen_ignores_sync_item_1_and_sentinel(self, mock_get_output_instance):
+        mock_component = mock.MagicMock()
+        mock_target = mock.MagicMock()
+        mock_component.store = mock_target
+        mock_get_output_instance.return_value = mock_component
+        target = "store"
+        output_config = {"random_name": {"type": "dummy_output"}}
+        queue = ThrottlingQueue(multiprocessing.get_context(), 100)
+        listener = OutputQueueListener(queue, target, output_config)
+        listener.queue.put(1)
+        listener.queue.put(listener.sentinel)
+        listener._listen()
+        mock_target.assert_not_called()
+
+    @mock.patch(
+        "logprep.framework.pipeline_manager.OutputQueueListener.get_output_instance",
+    )
+    @mock.patch("logging.Logger.error")
+    def test_listen_logs_event_on_unexpected_exception(self, mock_error, mock_get_output_instance):
+        mock_component = mock.MagicMock()
+        mock_target = mock.MagicMock()
+        mock_target.side_effect = Exception("TestException")
+        mock_component.store = mock_target
+        mock_get_output_instance.return_value = mock_component
+        target = "store"
+        output_config = {"random_name": {"type": "dummy_output"}}
+        queue = ThrottlingQueue(multiprocessing.get_context(), 100)
+        listener = OutputQueueListener(queue, target, output_config)
+        event = {"event": "test"}
+        listener.queue.put(event)
+        listener.queue.put(listener.sentinel)
+        time.sleep(0.1)  # test will sometimes fail without it, probably due to ThrottlingQueue
+        listener._listen()
+        expected_error_log = (
+            f"[Error Event] Couldn't enqueue error item due to: TestException | Item: '{event}'"
+        )
+        mock_error.assert_called_with(expected_error_log)
+
+    @mock.patch(
+        "logprep.framework.pipeline_manager.OutputQueueListener.get_output_instance",
+        new=mock.MagicMock(),
+    )
+    def test_drain_queue_ignores_sync_item_1_and_sentinel(self):
+        target = "store"
+        output_config = {"random_name": {"type": "dummy_output"}}
+        queue = ThrottlingQueue(multiprocessing.get_context(), 100)
+        listener = OutputQueueListener(queue, target, output_config)
+        listener.queue.put(1)
+        listener.queue.put(listener.sentinel)
+        mock_target = mock.MagicMock()
+        listener._drain_queue(mock_target)
+        mock_target.assert_not_called()
+
+    @mock.patch(
+        "logprep.framework.pipeline_manager.OutputQueueListener.get_output_instance",
+        new=mock.MagicMock(),
+    )
+    @mock.patch("logging.Logger.error")
+    def test_drain_queue_logs_event_on_unexpected_exception(self, mock_error):
+        target = "store"
+        output_config = {"random_name": {"type": "dummy_output"}}
+        queue = ThrottlingQueue(multiprocessing.get_context(), 100)
+        listener = OutputQueueListener(queue, target, output_config)
+        event = {"event": "test"}
+        listener.queue.put(event)
+        mock_target = mock.MagicMock()
+        mock_target.side_effect = Exception("TestException")
+        time.sleep(0.1)  # test will sometimes fail without it, probably due to ThrottlingQueue
+        listener._drain_queue(mock_target)
+        expected_error_log = (
+            f"[Error Event] Couldn't enqueue error item due to: TestException | Item: '{event}'"
+        )
+        mock_error.assert_called_with(expected_error_log)