test: fix DummyLokiHandler emit to avoid NotImplementedError (refs #6)

Author: pmcfadin

tests/utils/test_logging_handlers.py

@@ -0,0 +1,60 @@
+import importlib
+import logging
+from types import ModuleType
+
+import pytest
+from fastapi import FastAPI
+
+from app.core import config as cfg
+
+
+@pytest.mark.parametrize("loki_enabled", [True, False])
+def test_logging_handler_selection(tmp_path, monkeypatch, loki_enabled):
+    """When Loki enabled and lib present we attach LokiHandler, else RotatingFileHandler."""
+
+    # Temp log dir
+    monkeypatch.chdir(tmp_path)
+
+    # Patch settings at runtime
+    monkeypatch.setattr(cfg.settings, "LOKI_ENABLED", loki_enabled, raising=False)
+    monkeypatch.setattr(
+        cfg.settings, "LOKI_ENDPOINT", "http://dummy:3100", raising=False
+    )
+
+    # Reset root handlers to avoid cross-param contamination
+    logging.getLogger().handlers.clear()
+
+    # Re-import observability to reset flags
+    obs = importlib.reload(importlib.import_module("app.utils.observability"))
+
+    # Monkeypatch logging_loki availability based on scenario
+    if loki_enabled:
+
+        class DummyLokiHandler(logging.Handler):
+            def __init__(self, *args, **kwargs):  # accept arbitrary Loki kwargs
+                super().__init__()
+
+            def emit(self, record):  # noqa: D401
+                # Simply drop log records in tests
+                return
+
+        dummy_module = ModuleType("logging_loki")
+        dummy_module.LokiHandler = DummyLokiHandler  # type: ignore[attr-defined]
+        monkeypatch.setitem(importlib.sys.modules, "logging_loki", dummy_module)
+        obs._LOKI_READY = True  # type: ignore[attr-defined]
+    else:
+        # Ensure module import fails
+        if "logging_loki" in importlib.sys.modules:
+            del importlib.sys.modules["logging_loki"]
+        obs._LOKI_READY = False  # type: ignore[attr-defined]
+
+    # Run configurator
+    app = FastAPI()
+    obs.configure_observability(app)
+
+    handler_types = {type(h).__name__ for h in logging.getLogger().handlers}
+
+    if loki_enabled:
+        assert "DummyLokiHandler" in handler_types
+    else:
+        assert "RotatingFileHandler" in handler_types