diff --git a/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py b/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
index 390905a6..de8218cf 100644
--- a/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
+++ b/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
@@ -38,7 +38,10 @@ from backend.documents_parser.elmhurst_extractor import ElmhurstSiteNotesExtract
 from datatypes.epc.domain.mapper import EpcPropertyDataMapper
 from domain.sap.calculator import calculate_sap_from_inputs
 from domain.sap.rdsap.cert_to_inputs import SAP_10_2_SPEC_PRICES, cert_to_inputs
-from domain.sap.worksheet.tests import _elmhurst_worksheet_000474 as _w000474
+from domain.sap.worksheet.tests import (
+    _elmhurst_worksheet_000474 as _w000474,
+    _elmhurst_worksheet_000477 as _w000477,
+)
 
 _FIXTURES = Path(__file__).parent / "fixtures"
 _SUMMARY_000474_PDF = _FIXTURES / "Summary_000474.pdf"
@@ -564,3 +567,33 @@ def test_from_elmhurst_site_notes_matches_hand_built_000474() -> None:
         f"hand-built EpcPropertyData for cohort cert 000474:\n  " +
         "\n  ".join(diffs)
     )
+
+
+def test_from_elmhurst_site_notes_matches_hand_built_000477() -> None:
+    # Arrange — _elmhurst_worksheet_000477.build_epc() is the canonical
+    # hand-built EpcPropertyData for cert U985-0001-000477 (single-bp
+    # mid-terrace, age band B, RIR with stud walls + party gables, no
+    # extension); it cascades to the worksheet PDF's `SAP value 65.0057`
+    # at 1e-4. Routing the Summary PDF through the Elmhurst mapper MUST
+    # produce a load-bearing-field-equivalent EpcPropertyData; any
+    # divergence is a mapper-coverage gap to close as its own slice.
+    pages = _summary_pdf_to_textract_style_pages(_SUMMARY_000477_PDF)
+    site_notes = ElmhurstSiteNotesExtractor(pages).extract()
+    mapped = EpcPropertyDataMapper.from_elmhurst_site_notes(site_notes)
+    hand_built = _w000477.build_epc()
+
+    # Act
+    diffs: list[str] = []
+    for field_name in _LOAD_BEARING_FIELDS:
+        diffs.extend(_diff_load_bearing(
+            getattr(mapped, field_name, None),
+            getattr(hand_built, field_name, None),
+            field_name,
+        ))
+
+    # Assert
+    assert not diffs, (
+        f"{len(diffs)} load-bearing divergence(s) between mapped and "
+        f"hand-built EpcPropertyData for cohort cert 000477:\n  " +
+        "\n  ".join(diffs)
+    )