Unit tests for osism/settings.py

[berendt]

Background

Follow-up to #2192 (foundation) and PR #2193 (pytest + Zuul infrastructure). osism/settings.py reads configuration from environment variables and from Docker secrets in /run/secrets/. Defaults are important here because they determine behavior when an operator forgets to set a variable — so they deserve a regression test.

Scope

Add tests/unit/test_settings.py covering the read_secret helper and the module-level settings in osism/settings.py.

Test targets

read_secret(secret_name) — osism/settings.py:6

• Existing file under /run/secrets/<name> with content \"abc\\n\" → returns \"abc\" (trailing newline stripped)
• File does not exist → returns \"\" (not None)
• File is empty → returns \"\"
• File has leading/trailing whitespace on the first line → only trailing is stripped via .strip() (verify exact behavior matches implementation)

Use tmp_path and monkeypatch to redirect the /run/secrets/ path — the cleanest approach is monkeypatch.setattr(\"builtins.open\", ...) or refactor-free: pass a tmp_path-based path via monkeypatch.setattr of a helper. If that proves intrusive, it is acceptable to test by actually creating /run/secrets/ is not acceptable — use mocking instead.

Module-level settings

Because settings are read at import time, tests need to re-import osism.settings under controlled environments. The pattern:

import importlib
import osism.settings as settings_module

def test_default_redis_host(monkeypatch):
    monkeypatch.delenv(\"REDIS_HOST\", raising=False)
    importlib.reload(settings_module)
    assert settings_module.REDIS_HOST == \"redis\"

Required cases (pick representatives, not every single var):

Variable	Default	Override test
REDIS_HOST	\"redis\"	REDIS_HOST=mycache → \"mycache\"
REDIS_PORT	6379 (int)	REDIS_PORT=1234 → 1234 (int)
REDIS_DB	0 (int)	REDIS_DB=5 → 5
IGNORE_SSL_ERRORS	True	IGNORE_SSL_ERRORS=False → False; any other string → False
GATHER_FACTS_SCHEDULE	43200.0 (float)	GATHER_FACTS_SCHEDULE=60 → 60.0
FACTS_MAX_AGE	equals int of GATHER_FACTS_SCHEDULE when unset	explicit override honored
INVENTORY_RECONCILER_SCHEDULE	600.0	override honored
OPERATOR_USER	\"dragon\"	OSISM_OPERATOR_USER=admin → \"admin\"
FRR_DUMMY_INTERFACE	\"loopback0\"	OSISM_FRR_DUMMY_INTERFACE=lo1 → \"lo1\"
NETBOX_URL	None	NETBOX_API beats NETBOX_URL when both set (verify precedence in os.getenv(\"NETBOX_API\", os.getenv(\"NETBOX_URL\")))
NETBOX_TOKEN	\"\"	env var wins over secret file; falls back to read_secret when env is unset; .strip() applied
SONIC_EXPORT_DIR / SONIC_EXPORT_PREFIX / SONIC_EXPORT_SUFFIX / SONIC_EXPORT_IDENTIFIER	string defaults	override honored
NETBOX_SECONDARIES	\"[]\"	env wins; read_secret fallback; literal default when both absent
REDFISH_TIMEOUT	20 (int)	override honored
NETBOX_MAX_CONNECTIONS	5 (int)	override honored

NETBOX_FILTER_CONDUCTOR_IRONIC / NETBOX_FILTER_CONDUCTOR_SONIC

• Defaults are the literal strings documented in settings.py:44-51
• Override via env is honored

Mocking hints

• Use monkeypatch.setenv / monkeypatch.delenv and importlib.reload(osism.settings) per test. Restore the module at the end of the test module via an autouse fixture so later tests see the original state.
• For read_secret, mock the open(...) call or monkeypatch a path constant if you extract one; do not write to /run/secrets/ on the host.

Definition of Done

• tests/unit/test_settings.py created
• All listed settings have at least a default-value test; overrides are covered for one representative per type (str/int/float/bool)
• read_secret has tests for happy path, missing file, and whitespace handling
• pipenv run pytest tests/unit/test_settings.py passes locally
• Tests do not leak env vars to subsequent tests (verify with pipenv run pytest on the whole suite)
• flake8, mypy, python-black remain green
• Zuul job python-osism-unit-tests passes

Dependencies

• Part of Meta: Unit test coverage for osism/ #2199 (meta). Blocked by Introduce foundation for unit tests (pytest + Zuul CI integration) #2192 / PR Introduce foundation for unit tests (pytest + Zuul CI) #2193