basic structure for lazy config loading

tests/_test_data/dopt-cfg.toml

@@ -0,0 +1,2 @@
+[forecast]
+threshold_month_data_points = 28

tests/conftest.py

@@ -33,6 +33,15 @@ def api_base_url(credentials) -> str:
     return credentials["base_url"]
 
 
+@pytest.fixture(scope="session")
+def pth_dummy_cfg() -> Path:
+    pwd = Path.cwd()
+    assert "barth" in pwd.parent.name.lower(), "not in project root directory"
+    data_pth = pwd / "./tests/_test_data/dopt-cfg.toml"
+    assert data_pth.exists(), "file to dummy CFG not found"
+    return data_pth
+
+
 @pytest.fixture(scope="session")
 def sales_data_real() -> pd.DataFrame:
     pwd = Path.cwd()

tests/test_config.py

@@ -0,0 +1,58 @@
+import tomllib
+from pathlib import Path
+
+import pytest
+import tomli_w
+
+from delta_barth import config
+
+
+@pytest.fixture(scope="function")
+def pth_cfg(pth_dummy_cfg, tmp_path) -> Path:
+    with open(pth_dummy_cfg, "rb") as file:
+        cfg_data = tomllib.load(file)
+
+    target = tmp_path / "dummy_cfg.toml"
+    target.touch()
+    with open(target, "wb") as file:
+        tomli_w.dump(cfg_data, file)
+
+    return target
+
+
+@pytest.mark.new
+def test_CfgLoader_Init(pth_cfg):
+    loader = config.LazyCfgLoader(pth_cfg)
+
+    assert loader.path == pth_cfg
+    assert loader._cfg is None
+
+
+@pytest.mark.new
+def test_CfgLoader_Get(pth_cfg):
+    loader = config.LazyCfgLoader(pth_cfg)
+
+    parsed_cfg = loader.get()
+    assert isinstance(parsed_cfg, config.Config)
+    assert parsed_cfg.forecast.threshold_month_data_points == 28
+
+
+@pytest.mark.new
+def test_CfgLoader_Reload(pth_cfg):
+    loader = config.LazyCfgLoader(pth_cfg)
+
+    parsed_cfg = loader.get()
+    assert isinstance(parsed_cfg, config.Config)
+    assert parsed_cfg.forecast.threshold_month_data_points == 28
+    # modify config and reload
+    with open(pth_cfg, "rb") as file:
+        cfg_data = tomllib.load(file)
+    cfg_data["forecast"]["threshold_month_data_points"] = 30
+    with open(pth_cfg, "wb") as file:
+        tomli_w.dump(cfg_data, file)
+
+    assert parsed_cfg.forecast.threshold_month_data_points == 28
+    loader.reload()
+    parsed_cfg = loader.get()
+    assert isinstance(parsed_cfg, config.Config)
+    assert parsed_cfg.forecast.threshold_month_data_points == 30