feat(sp41): CARC-aware filter — CO-45/26/129 excluded, PI-16/OA-18 reviewed

backend/tests/test_rebill_carc_filter.py

@@ -0,0 +1,49 @@
+"""CARC-aware filter for Pipeline A.
+
+Contractual / non-recoverable denials (CO-45, CO-26, CO-129) must be
+excluded from rebill. CARCs that need operator review (PI-16, PI-96,
+PI-15, PI-4, PI-110, OA-18, OA-23) must be surfaced as 'REVIEW' so the
+operator can decide.
+"""
+from cyclone.rebill.carc_filter import (
+    CarcDecision,
+    decide_carc,
+    EXCLUDED_CARCS,
+    REVIEW_CARCS,
+)
+
+
+def test_co45_is_excluded():
+    assert decide_carc(("CO-45",)) == CarcDecision.EXCLUDED
+
+
+def test_co26_is_excluded():
+    assert decide_carc(("CO-26",)) == CarcDecision.EXCLUDED
+
+
+def test_co129_is_excluded():
+    assert decide_carc(("CO-129",)) == CarcDecision.EXCLUDED
+
+
+def test_pi16_is_review():
+    assert decide_carc(("PI-16",)) == CarcDecision.REVIEW
+
+
+def test_o18_is_review():
+    """OA-18 is the duplicate noise — surface for review, don't auto-rebill."""
+    assert decide_carc(("OA-18",)) == CarcDecision.REVIEW
+
+
+def test_no_carc_is_rebill():
+    assert decide_carc(()) == CarcDecision.REBILL
+
+
+def test_mixed_excluded_wins():
+    """If any CARC is excluded, the whole service is excluded."""
+    assert decide_carc(("PI-16", "CO-45")) == CarcDecision.EXCLUDED
+
+
+def test_sets_have_expected_members():
+    assert "CO-45" in EXCLUDED_CARCS
+    assert "PI-16" in REVIEW_CARCS
+    assert "OA-18" in REVIEW_CARCS