fix: tolerate spreadsheet decimal roundoff

tests/test_monthly_reports_xlsx.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 
 import tempfile
 import unittest
-from datetime import date
+from datetime import date, timedelta
 from decimal import Decimal
 from pathlib import Path
 
@@ -13,6 +13,7 @@ from monthly_reports.contracts import (
     DailyVersionPin,
     MonthlyFact,
     MonthlySnapshot,
+    STANDARD_SHEETS,
 )
 from monthly_reports.core import build_monthly_report
 from monthly_reports.publishing import OpenpyxlWorkbookBuilder
@@ -57,6 +58,77 @@ def report_fixture():
     )
 
 
+def large_decimal_report_fixture():
+    facts = []
+    daily_versions = []
+    channel_observations = []
+    record_id = 1000
+    daily_plan = (
+        (date(2026, 8, 1), 501, 28),
+        (date(2026, 8, 2), 502, 30),
+        (date(2026, 8, 3), 503, 30),
+    )
+    for business_date, daily_version_id, rows_per_sheet in daily_plan:
+        daily_versions.append(DailyVersionPin(business_date, daily_version_id))
+        for channel_index, channel_key in enumerate(STANDARD_SHEETS, start=1):
+            channel_observations.append(
+                ChannelObservation(
+                    business_date,
+                    daily_version_id,
+                    channel_key,
+                    channel_index,
+                    rows_per_sheet,
+                )
+            )
+            for row_index in range(rows_per_sheet):
+                nights = 1 + (row_index % 3)
+                no_of_rooms = 1 + (row_index % 2)
+                real_price = Decimal("321.17") + Decimal(row_index % 19) / Decimal("100")
+                sequence = record_id
+                facts.append(
+                    MonthlyFact(
+                        daily_record_id=sequence,
+                        daily_version_id=daily_version_id,
+                        business_date=business_date,
+                        channel_key=channel_key,
+                        arrival=business_date,
+                        departure=business_date + timedelta(days=nights),
+                        nights=nights,
+                        adults=2,
+                        children=row_index % 2,
+                        block_code=f"BLOCK-{sequence}",
+                        no_of_rooms=no_of_rooms,
+                        company_name=f"COMPANY-{channel_index}",
+                        confirmation_no=f"CONF-{sequence}",
+                        disp_room_no=f"ROOM-{sequence}",
+                        effective_rate_amount=Decimal("247.35")
+                        + Decimal((row_index + channel_index) % 7) / Decimal("100"),
+                        full_name=f"GUEST-{sequence}",
+                        res_comment=f"COMMENT-{sequence}",
+                        trace_text="TRACE",
+                        products="ROOM",
+                        rate_code="BAR",
+                        room_category_label="STD",
+                        real_price=real_price,
+                        total_price=real_price * no_of_rooms * nights,
+                        kb_amount=Decimal(no_of_rooms * 100)
+                        if channel_key == "DY-AI-Easy-KB"
+                        else None,
+                    )
+                )
+                record_id += 1
+    return build_monthly_report(
+        2026,
+        8,
+        date(2026, 8, 3),
+        MonthlySnapshot(
+            tuple(facts),
+            tuple(daily_versions),
+            tuple(channel_observations),
+        ),
+    )
+
+
 class MonthlyReportsXlsxTests(unittest.TestCase):
     def test_openpyxl_builder_reopens_checks_formulas_and_semantic_identity(self):
         report = report_fixture()
@@ -88,6 +160,31 @@ class MonthlyReportsXlsxTests(unittest.TestCase):
             finally:
                 workbook.close()
 
+    def test_openpyxl_builder_validates_440_decimal_rows_across_multiple_sheets(self):
+        report = large_decimal_report_fixture()
+        self.assertEqual(report.row_count, 440)
+
+        with tempfile.TemporaryDirectory(prefix="monthly-report-xlsx-large-") as temp_dir:
+            built = OpenpyxlWorkbookBuilder().build(report, Path(temp_dir))
+
+            self.assertEqual(built.summary["sheet_names"], list(STANDARD_SHEETS))
+            self.assertEqual(built.summary["row_counts"], [88, 88, 88, 88, 88])
+            self.assertEqual(built.summary["formula_count"], 440)
+            self.assertTrue(
+                OpenpyxlWorkbookBuilder._decimal_matches("321.1700005", "321.17")
+            )
+            self.assertFalse(
+                OpenpyxlWorkbookBuilder._decimal_matches("321.1700011", "321.17")
+            )
+            self.assertEqual(
+                OpenpyxlWorkbookBuilder._validate_workbook(
+                    built.path,
+                    report,
+                    report.to_workbook_payload(),
+                ),
+                440,
+            )
+
 
 if __name__ == "__main__":
     unittest.main()