🧪 [Add tests for load_persisted_stats]

router/tests/test_load_persisted_stats.py

@@ -0,0 +1,61 @@
+import json
+import pytest
+from unittest.mock import patch, mock_open
+
+import router.main
+from router.main import load_persisted_stats
+
+@pytest.fixture
+def mock_stats():
+    # Setup a clean stats dictionary for testing
+    clean_stats = {
+        "total_requests": 0,
+        "nested_dict": {"a": 1, "b": 2},
+        "existing_key": "value"
+    }
+    with patch.dict(router.main.stats, clean_stats, clear=True):
+        yield router.main.stats
+
+def test_load_persisted_stats_file_not_exists(mock_stats):
+    with patch("router.main.os.path.exists", return_value=False) as mock_exists:
+        load_persisted_stats()
+        mock_exists.assert_called_once_with(router.main.STATS_JSON_PATH)
+        # Stats should remain unchanged
+        assert mock_stats["total_requests"] == 0
+
+def test_load_persisted_stats_success(mock_stats):
+    mock_data = {
+        "total_requests": 100,
+        "nested_dict": {"b": 3, "c": 4},
+        "new_key": "new_value"
+    }
+    mock_json = json.dumps(mock_data)
+
+    with patch("router.main.os.path.exists", return_value=True):
+        with patch("router.main.open", mock_open(read_data=mock_json)):
+            with patch("router.main.logger.info") as mock_logger:
+                load_persisted_stats()
+
+                # Assert simple value updated via else block
+                assert mock_stats["total_requests"] == 100
+                # Assert nested_dict updated via if block (b updated, c added, a unchanged)
+                assert mock_stats["nested_dict"] == {"a": 1, "b": 3, "c": 4}
+                # Assert new_key added via else block
+                assert mock_stats["new_key"] == "new_value"
+                # Assert existing_key unchanged
+                assert mock_stats["existing_key"] == "value"
+
+                mock_logger.assert_called_once_with("✓ Successfully loaded persisted gateway statistics from disk.")
+
+def test_load_persisted_stats_exception(mock_stats):
+    with patch("router.main.os.path.exists", return_value=True):
+        with patch("router.main.open", side_effect=Exception("Mock read error")):
+            with patch("router.main.logger.error") as mock_logger:
+                load_persisted_stats()
+
+                # Stats should remain unchanged
+                assert mock_stats["total_requests"] == 0
+
+                # Error should be logged
+                mock_logger.assert_called_once()
+                assert "Failed to load persisted stats: Mock read error" in mock_logger.call_args[0][0]