feat(sp41): serialize_837 overload for member-week batches

backend/tests/test_rebill_pipeline_b.py

@@ -73,3 +73,48 @@ def test_override_flag_set_on_past_window_visit_batch():
     assert out_default[0].member_id == "OLD"
     assert out_default[0].iso_week == 26
     assert out_default[0].has_overridden_visits is False
+
+
+def test_serialize_member_week_batch_emits_one_envelope():
+    """One 837P envelope per MemberWeekBatch — one CLM + one SV1 + one
+    DTP*472 service date per visit.
+
+    The SP41 plan spec wrote ``DTM*472*`` but the canonical 837P service
+    date segment is ``DTP*472*`` (per :func:`cyclone.parsers.serialize_837.
+    _build_dtp_472` and X12 005010X222A1). This test asserts against the
+    canonical segment name so the batch overload stays consistent with
+    the existing ``serialize_837`` building blocks.
+    """
+    from cyclone.parsers.serialize_837 import serialize_member_week_batch
+    visits = [
+        _v(date(2026, 6, 23), "J813715", "T1019", "2.32"),
+        _v(date(2026, 6, 25), "J813715", "T1019", "2.32"),
+    ]
+    batches = build_pipeline_b_batches(visits, as_of=date(2026, 7, 7), override=False)
+    assert len(batches) == 1
+    body = serialize_member_week_batch(batches[0])
+    text = body.decode("utf-8", errors="ignore") if isinstance(body, bytes) else body
+    # CLM* segment appears twice (once per visit)
+    assert text.count("CLM*") == 2
+    # SV1* appears once per visit (one service line per claim)
+    assert text.count("SV1*") == 2
+    # DTP*472* service-date segment appears twice (canonical 837P segment name)
+    assert text.count("DTP*472*") == 2
+    # Single envelope (single ISA / single IEA), not per-visit envelopes
+    assert text.count("ISA*") == 1
+    assert text.count("IEA*") == 1
+    # Deterministic per-visit claim_id pattern (member_id + date + 1-based idx)
+    assert "MW-J813715-2026-06-23-01" in text
+    assert "MW-J813715-2026-06-25-02" in text
+
+
+def test_serialize_member_week_batch_return_type_is_bytes():
+    """Task 14 spec: ``serialize_member_week_batch`` returns ``bytes``
+    (the existing ``serialize_837`` returns ``str``; this overload
+    diverges intentionally so callers can write the file directly)."""
+    from cyclone.parsers.serialize_837 import serialize_member_week_batch
+    visits = [_v(date(2026, 6, 23), "J813715", "T1019", "2.32")]
+    batches = build_pipeline_b_batches(visits, as_of=date(2026, 7, 7), override=False)
+    assert len(batches) == 1
+    body = serialize_member_week_batch(batches[0])
+    assert isinstance(body, bytes)