informed-decision/tests/test_layer_conformance.py

"""Layer and stance conformance.

GH-DEC-2026-012 confirmed this repository is PEP-shaped and told it to build to
v0.8 obligation 3 rather than migrate to it later. These tests pin the parts of
that obligation a test can actually hold:

- the published map equals the shipped map (obligation 3, a MUST);
- the axis is enumerated, not defaulted;
- ``unknown`` resolves to ``fail_closed``;
- an absent scope is distinguishable in the record from an unknown one;
- the inherited GH-DEC-2026-010 attributability gap is declared open rather
  than described as satisfied.
"""

from __future__ import annotations

import pathlib

import pytest

yaml = pytest.importorskip("yaml")

from informed_decision.stance import AXIS, AXIS_VALUES, STANCE, BindingLevelState, resolve

ROOT = pathlib.Path(__file__).resolve().parents[1]


def load(name: str) -> dict:
    return yaml.safe_load((ROOT / name).read_text(encoding="utf-8"))


@pytest.fixture(scope="module")
def stance_doc() -> dict:
    return load("pep-stance.yaml")


@pytest.fixture(scope="module")
def layer_doc() -> dict:
    return load("layer.yaml")


# --------------------------------------------------------------------------
# Obligation 3 — published equals shipped. This is the MUST.
# --------------------------------------------------------------------------


def test_published_stance_equals_shipped_stance(stance_doc):
    assert stance_doc["stance"] == STANCE, (
        "pep-stance.yaml has drifted from informed_decision/stance.py. "
        "A published map that may differ from the code is worse than none."
    )


def test_published_axis_equals_shipped_axis(stance_doc):
    assert stance_doc["axis"] == AXIS


# --------------------------------------------------------------------------
# Obligation 3 — totality by enumeration, no catch-all, no implicit default.
# --------------------------------------------------------------------------


def test_every_axis_value_has_an_explicit_stance():
    for value in AXIS_VALUES:
        assert value in STANCE, f"{value} has no declared stance"


def test_stance_map_has_no_entries_beyond_the_axis_and_the_two_outcomes():
    allowed = set(AXIS_VALUES) | {"unknown", "absent"}
    assert set(STANCE) == allowed


def test_unknown_resolves_to_fail_closed(stance_doc):
    """v0.8 obligation 3 makes this a MUST; v0.7 permitted fail_open."""
    assert STANCE["unknown"] == "fail_closed"
    assert stance_doc["stance"]["unknown"] == "fail_closed"


@pytest.mark.parametrize("value", sorted(STANCE))
def test_no_stance_is_permissive(value):
    """Not required by the standard — required by this repository.

    Binding an identity without an authorization decision is the failure this
    surface exists to prevent, so there is no level at which proceeding is the
    safer error. If this test is ever relaxed, the reasoning in pep-stance.yaml
    must be rewritten first.
    """
    assert STANCE[value] == "fail_closed"


# --------------------------------------------------------------------------
# Obligation 3 — absent must be distinguishable from unknown IN THE RECORD,
# even though both resolve to the same stance.
# --------------------------------------------------------------------------


def test_absent_and_unknown_resolve_the_same_but_record_differently():
    absent_stance, absent_state = resolve(None)
    unknown_stance, unknown_state = resolve("notalevel")
    assert absent_stance == unknown_stance == "fail_closed"
    assert absent_state is BindingLevelState.ABSENT
    assert unknown_state is BindingLevelState.UNKNOWN
    assert absent_state != unknown_state


def test_empty_string_is_absent_not_unknown():
    assert resolve("")[1] is BindingLevelState.ABSENT


@pytest.mark.parametrize("value", AXIS_VALUES)
def test_known_axis_values_record_as_present(value):
    stance, state = resolve(value)
    assert state is BindingLevelState.PRESENT
    assert stance == "fail_closed"


def test_published_map_declares_the_two_states_distinguishable(stance_doc):
    absence = stance_doc["scope_absence"]
    assert absence["distinguishable"] is True
    assert absence["recorded_as"]["absent"] != absence["recorded_as"]["unknown"]


# --------------------------------------------------------------------------
# Inherited gap — GH-DEC-2026-010. Must be declared open, not glossed.
# --------------------------------------------------------------------------


def test_attributability_gap_is_declared_open_in_the_stance(stance_doc):
    gap = stance_doc["inherited_gap"]
    assert gap["decision_attributable_today"] is False
    assert gap["tracked_by"] == "FLEX-WP-0024"


def test_attributability_gap_is_declared_open_in_the_layer(layer_doc):
    gaps = {g["id"]: g for g in layer_doc["inherited_gaps"]}
    gap = gaps["GH-DEC-2026-010-attributability"]
    assert gap["status"] == "open"


def test_stance_records_whether_the_decision_was_attributable(stance_doc):
    assert "decision_attributable" in stance_doc["on_apply"]["recorded_fields"]


# --------------------------------------------------------------------------
# R1 / R2 / R3 — the ruling's limits are declared, not merely remembered.
# --------------------------------------------------------------------------


def test_layer_declares_pep_shaped_and_no_decision_surface(layer_doc):
    assert layer_doc["role"] == "pep-shaped"
    assert layer_doc["decision_surfaces_exposed"] == "none"


def test_presentation_claim_carries_all_three_limits(layer_doc):
    limits = {limit["id"] for limit in layer_doc["presentation_claim"]["limits"]}
    assert limits == {
        "L1-presentation-only",
        "L2-not-an-input",
        "L3-independent-evidence-path",
    }


def test_binding_digest_relationship_is_co_reference_not_nesting(layer_doc):
    rel = layer_doc["binding_digest_relationship"]
    assert rel["linkage"] == "co-reference"
    assert rel["substitutable"] is False
    assert "nesting_forbidden" in rel


def test_residual_is_declared_not_closed(layer_doc):
    assert layer_doc["evidence"]["residual_closed"] is False


# --------------------------------------------------------------------------
# §13.1 / GH-DEC-2026-011 — a dated coverage figure beside the stance.
# --------------------------------------------------------------------------


def test_classification_coverage_is_dated_and_complete_against_the_axis(stance_doc):
    cov = stance_doc["classification_coverage"]
    assert cov["as_of"]
    assert cov["axis_values_enumerated"] == cov["axis_values_in_schema"] == len(AXIS_VALUES)