school_compare/backend/tests/test_flags.py

"""Tests for the feature flag layer (spec 2026-08-23).

None of these need a running Unleash. That is the point: an unset UNLEASH_URL
means every flag is False, which is what local development and CI get.
"""

from datetime import date, timedelta

from backend import flags


def test_every_declared_flag_is_keyed_by_its_own_name():
    # One string is the registry key, the Unleash flag name and the JSON key.
    # A mismatch here would mean the UI toggles a flag the code never reads.
    for key, flag in flags.REGISTRY.items():
        assert key == flag.name


def test_flag_names_are_snake_case():
    # Matches the API's existing convention (admission_distance,
    # rwm_expected_pct) so no case transformation exists to get wrong.
    for name in flags.REGISTRY:
        assert name == name.lower()
        assert "-" not in name and " " not in name


def test_an_unconfigured_client_evaluates_every_flag_false(monkeypatch):
    monkeypatch.setattr(flags, "_client", None)
    for name in flags.REGISTRY:
        assert flags.is_enabled(name) is False


def test_an_undeclared_flag_is_false_rather_than_an_error(monkeypatch):
    # A typo'd flag name must not raise in a request path. It is logged as an
    # error, because an undeclared flag is always a bug.
    monkeypatch.setattr(flags, "_client", None)
    assert flags.is_enabled("no_such_flag") is False


def test_an_exploding_client_is_false_rather_than_a_500(monkeypatch):
    class Boom:
        def is_enabled(self, *a, **kw):
            raise RuntimeError("unleash is on fire")

    monkeypatch.setattr(flags, "_client", Boom())
    name = next(iter(flags.REGISTRY))
    assert flags.is_enabled(name) is False


def test_all_flags_reports_every_declared_flag(monkeypatch):
    monkeypatch.setattr(flags, "_client", None)
    assert set(flags.all_flags()) == set(flags.REGISTRY)
    assert all(v is False for v in flags.all_flags().values())


def test_a_flag_older_than_the_limit_fails_this_test():
    """A tripwire, not an assertion about correctness.

    Flags are temporary scaffolding and the failure mode of every flag system
    is accumulation. This fails on the day a flag turns 90, on whatever PR
    happens to be open — which is the point: someone has to decide.

    To fix: delete the flag and the branches that read it, or, if it genuinely
    still needs to exist, move its `added` date and say why in the commit.
    """
    stale = [
        f.name for f in flags.REGISTRY.values()
        if date.today() - f.added > timedelta(days=flags.MAX_FLAG_AGE_DAYS)
    ]
    assert not stale, (
        f"Flags older than {flags.MAX_FLAG_AGE_DAYS} days: {stale}. "
        "Remove the flag and the code branches it guards, or move its `added` "
        "date deliberately."
    )


def _client():
    from fastapi.testclient import TestClient
    from backend import app as app_module
    return TestClient(app_module.app, raise_server_exceptions=False)


def test_the_flags_endpoint_lists_every_declared_flag(monkeypatch):
    monkeypatch.setattr(flags, "_client", None)
    body = _client().get("/api/flags").json()
    assert set(body) == set(flags.REGISTRY)


def test_the_flags_endpoint_answers_false_when_unleash_is_unreachable(monkeypatch):
    # The endpoint must still answer. A frontend that cannot read flags renders
    # everything dark, which is right; one that gets a 500 renders nothing.
    monkeypatch.setattr(flags, "_client", None)
    res = _client().get("/api/flags")
    assert res.status_code == 200
    assert all(v is False for v in res.json().values())