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 5b7267e7..94a3b927 100644
--- a/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
+++ b/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
@@ -1,6 +1,6 @@
 """End-to-end validation for the Elmhurst Summary→EpcPropertyData chain.
 
-The 6 Elmhurst worksheet fixtures in `domain.sap10_calculator.worksheet.tests`
+The 6 Elmhurst worksheet fixtures in `tests.domain.sap10_calculator.worksheet`
 build their `EpcPropertyData` synthetically — they validate the
 calculator + cascade in isolation from the mapper. This file pins
 the OTHER half of the chain: `from_elmhurst_site_notes` must produce
@@ -46,7 +46,7 @@ from datatypes.epc.domain.mapper import (
 from domain.sap10_calculator.calculator import calculate_sap_from_inputs
 from domain.sap10_calculator.rdsap.cert_to_inputs import SAP_10_2_SPEC_PRICES, cert_to_inputs
 from domain.sap10_ml.rdsap_uvalues import u_party_wall
-from domain.sap10_calculator.worksheet.tests import (
+from tests.domain.sap10_calculator.worksheet import (
     _elmhurst_worksheet_000474 as _w000474,
     _elmhurst_worksheet_000477 as _w000477,
     _elmhurst_worksheet_000480 as _w000480,
@@ -84,7 +84,7 @@ _SUMMARY_000565_PDF = _FIXTURES / "Summary_000565.pdf"  # cert 000565 (5-bp Elmh
 # matches worksheet continuous SAP at 1e-4".
 _API_001479_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "0535-9020-6509-0821-6222.json"
 )
 
@@ -129,7 +129,7 @@ def _summary_pdf_to_textract_style_pages(pdf_path: Path) -> list[str]:
 def test_summary_000474_mapper_produces_three_building_parts() -> None:
     # Arrange — cert U985-0001-000474 is a mid-terrace with 3 building
     # parts (Main + 2 extensions) per the hand-built worksheet fixture
-    # at domain/sap10_calculator/worksheet/tests/
+    # at tests/domain/sap10_calculator/worksheet/
     # _elmhurst_worksheet_000474.py. Routing the Summary PDF through
     # extractor + mapper must yield the same count.
     pages = _summary_pdf_to_textract_style_pages(_SUMMARY_000474_PDF)
@@ -2978,7 +2978,7 @@ def test_summary_mapper_raises_on_unmapped_party_wall_type_code() -> None:
 
 _GOLDEN_FIXTURES_DIR = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
 )
 
 
@@ -3292,13 +3292,13 @@ def test_summary_0380_full_chain_sap_within_spec_floor_of_worksheet() -> None:
 
 _API_0330_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "0330-2249-8150-2326-4121.json"
 )
 
 _API_9501_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "9501-3059-8202-7356-0204.json"
 )
 
@@ -3358,7 +3358,7 @@ def test_api_9501_photovoltaic_array_surfaced() -> None:
 
 _API_0380_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "0380-2471-3250-2596-8761.json"
 )
 
@@ -3479,20 +3479,20 @@ def test_api_0380_heat_pump_no_pumps_fans_kwh_per_table_4f() -> None:
 
 _API_9418_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "9418-3062-8205-3566-7200.json"
 )
 
 
 _API_2225_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "2225-3062-8205-2856-7204.json"
 )
 
 _API_2636_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "2636-0525-2600-0401-2296.json"
 )
 
@@ -3765,17 +3765,17 @@ def test_api_001479_full_chain_sap_matches_worksheet_pdf_exactly() -> None:
 
 _API_0350_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "0350-2968-2650-2796-5255.json"
 )
 _API_3800_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "3800-8515-0922-3398-3563.json"
 )
 _API_9285_JSON = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
     / "9285-3062-0205-7766-7200.json"
 )
 
@@ -3878,7 +3878,7 @@ def test_api_9418_full_chain_sap_within_spec_floor_of_worksheet() -> None:
 # SAP cascade is the load-bearing equivalence check. Each cert in this
 # cohort has both a Summary PDF (under `sap worksheets/additional with
 # api 2/<cert>/Summary_*.pdf`) and an API JSON fixture (fetched into
-# `domain/sap10_calculator/rdsap/tests/fixtures/golden/<cert>.json` in
+# `tests/domain/sap10_calculator/rdsap/fixtures/golden/<cert>.json` in
 # Slice S0380.39). Worksheet SAP is the source of truth.
 #
 # Cohort-2 API-path closure history (each slice closed a distinct
@@ -3893,7 +3893,7 @@ def test_api_9418_full_chain_sap_within_spec_floor_of_worksheet() -> None:
 
 _COHORT_2_API_FIXTURE_DIR: Path = (
     Path(__file__).parents[3]
-    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "tests/domain/sap10_calculator/rdsap/fixtures/golden"
 )
 
 # (cert_dir, worksheet_unrounded_sap) — 34 cohort-2 certs whose API-path
diff --git a/scripts/fetch_cohort2_api_jsons.py b/scripts/fetch_cohort2_api_jsons.py
index 70211453..5b764f50 100644
--- a/scripts/fetch_cohort2_api_jsons.py
+++ b/scripts/fetch_cohort2_api_jsons.py
@@ -1,7 +1,7 @@
 """Throwaway one-off: bulk-fetch cohort-2 EPC API JSONs from gov.uk EPB.
 
 Persists the inner `data` payload (as returned by EpcClientService._fetch_certificate)
-to domain/sap10_calculator/rdsap/tests/fixtures/golden/<cert>.json. Skips certs
+to tests/domain/sap10_calculator/rdsap/fixtures/golden/<cert>.json. Skips certs
 whose JSON already exists.
 """
 from __future__ import annotations
diff --git a/domain/sap10_calculator/climate/tests/__init__.py b/tests/domain/sap10_calculator/__init__.py
similarity index 100%
rename from domain/sap10_calculator/climate/tests/__init__.py
rename to tests/domain/sap10_calculator/__init__.py
diff --git a/domain/sap10_calculator/rdsap/tests/__init__.py b/tests/domain/sap10_calculator/climate/__init__.py
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/__init__.py
rename to tests/domain/sap10_calculator/climate/__init__.py
diff --git a/domain/sap10_calculator/climate/tests/test_appendix_u.py b/tests/domain/sap10_calculator/climate/test_appendix_u.py
similarity index 100%
rename from domain/sap10_calculator/climate/tests/test_appendix_u.py
rename to tests/domain/sap10_calculator/climate/test_appendix_u.py
diff --git a/domain/sap10_calculator/tests/__init__.py b/tests/domain/sap10_calculator/rdsap/__init__.py
similarity index 100%
rename from domain/sap10_calculator/tests/__init__.py
rename to tests/domain/sap10_calculator/rdsap/__init__.py
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0036-6325-1100-0063-1226.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0036-6325-1100-0063-1226.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0036-6325-1100-0063-1226.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0036-6325-1100-0063-1226.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0100-5141-0522-4696-3463.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0100-5141-0522-4696-3463.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0100-5141-0522-4696-3463.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0100-5141-0522-4696-3463.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0200-3155-0122-2602-3563.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0200-3155-0122-2602-3563.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0200-3155-0122-2602-3563.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0200-3155-0122-2602-3563.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0240-0200-5706-2365-8010.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0240-0200-5706-2365-8010.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0240-0200-5706-2365-8010.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0240-0200-5706-2365-8010.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0300-2403-2650-2206-0235.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0300-2403-2650-2206-0235.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0300-2403-2650-2206-0235.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0300-2403-2650-2206-0235.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0300-2747-7640-2526-2135.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0300-2747-7640-2526-2135.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0300-2747-7640-2526-2135.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0300-2747-7640-2526-2135.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0310-2763-5450-2506-3501.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0310-2763-5450-2506-3501.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0310-2763-5450-2506-3501.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0310-2763-5450-2506-3501.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0320-2126-2150-2326-6161.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0320-2126-2150-2326-6161.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0320-2126-2150-2326-6161.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0320-2126-2150-2326-6161.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0320-2756-8640-2296-1101.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0320-2756-8640-2296-1101.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0320-2756-8640-2296-1101.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0320-2756-8640-2296-1101.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0330-2249-8150-2326-4121.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0330-2249-8150-2326-4121.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0330-2249-8150-2326-4121.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0330-2249-8150-2326-4121.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0330-2257-3640-2196-3145.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0330-2257-3640-2196-3145.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0330-2257-3640-2196-3145.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0330-2257-3640-2196-3145.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0350-2968-2650-2796-5255.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0350-2968-2650-2796-5255.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0350-2968-2650-2796-5255.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0350-2968-2650-2796-5255.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0360-2266-5650-2106-8285.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0360-2266-5650-2106-8285.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0360-2266-5650-2106-8285.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0360-2266-5650-2106-8285.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0380-2471-3250-2596-8761.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0380-2471-3250-2596-8761.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0380-2471-3250-2596-8761.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0380-2471-3250-2596-8761.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0380-2530-6150-2326-4161.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0380-2530-6150-2326-4161.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0380-2530-6150-2326-4161.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0380-2530-6150-2326-4161.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0390-2066-4250-2026-4555.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0390-2066-4250-2026-4555.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0390-2066-4250-2026-4555.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0390-2066-4250-2026-4555.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0390-2254-6420-2126-5561.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0390-2254-6420-2126-5561.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/0390-2254-6420-2126-5561.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0390-2254-6420-2126-5561.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0390-2954-3640-2196-4175.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0390-2954-3640-2196-4175.json
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rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0390-2954-3640-2196-4175.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0464-3032-0205-4276-3204.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0464-3032-0205-4276-3204.json
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rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/0464-3032-0205-4276-3204.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0535-9020-6509-0821-6222.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0535-9020-6509-0821-6222.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/0652-3022-1205-2826-1200.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/0652-3022-1205-2826-1200.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/1536-9325-5100-0433-1226.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/1536-9325-5100-0433-1226.json
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rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/1536-9325-5100-0433-1226.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2007-3011-9205-8136-3204.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2007-3011-9205-8136-3204.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2031-3007-0205-1296-3204.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2031-3007-0205-1296-3204.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2102-3018-0205-7886-5204.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2102-3018-0205-7886-5204.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2130-1033-4050-5007-8395.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2130-1033-4050-5007-8395.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2130-3018-4205-4686-5204.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2130-3018-4205-4686-5204.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2225-3062-8205-2856-7204.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2225-3062-8205-2856-7204.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2336-3124-3600-0517-1292.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2336-3124-3600-0517-1292.json
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diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2536-2525-0600-0788-2292.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2536-2525-0600-0788-2292.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/2536-2525-0600-0788-2292.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/2536-2525-0600-0788-2292.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2590-3025-7205-9066-0200.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2590-3025-7205-9066-0200.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/2590-3025-7205-9066-0200.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/2590-3025-7205-9066-0200.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2636-0525-2600-0401-2296.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2636-0525-2600-0401-2296.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/2636-0525-2600-0401-2296.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/2636-0525-2600-0401-2296.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2699-3025-5205-8066-0200.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2699-3025-5205-8066-0200.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/2699-3025-5205-8066-0200.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/2699-3025-5205-8066-0200.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/2800-7999-0322-4594-3563.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/2800-7999-0322-4594-3563.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/2800-7999-0322-4594-3563.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/2800-7999-0322-4594-3563.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/3136-7925-4500-0246-6202.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/3136-7925-4500-0246-6202.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/3136-7925-4500-0246-6202.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/3136-7925-4500-0246-6202.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/3336-2825-9400-0512-8292.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/3336-2825-9400-0512-8292.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/3336-2825-9400-0512-8292.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/3336-2825-9400-0512-8292.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/3800-8515-0922-3398-3563.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/3800-8515-0922-3398-3563.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/3800-8515-0922-3398-3563.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/3800-8515-0922-3398-3563.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/4536-5424-8600-0109-1226.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/4536-5424-8600-0109-1226.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/4536-5424-8600-0109-1226.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/4536-5424-8600-0109-1226.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/4536-8325-3100-0409-1222.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/4536-8325-3100-0409-1222.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/4536-8325-3100-0409-1222.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/4536-8325-3100-0409-1222.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/4800-3992-0422-0599-3563.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/4800-3992-0422-0599-3563.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/4800-3992-0422-0599-3563.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/4800-3992-0422-0599-3563.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/6035-7729-2309-0879-2296.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/6035-7729-2309-0879-2296.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/6035-7729-2309-0879-2296.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/6035-7729-2309-0879-2296.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/6835-3920-2509-0933-5226.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/6835-3920-2509-0933-5226.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/6835-3920-2509-0933-5226.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/6835-3920-2509-0933-5226.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/7536-3827-0600-0600-0276.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/7536-3827-0600-0600-0276.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/7536-3827-0600-0600-0276.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/7536-3827-0600-0600-0276.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/7700-3362-0922-7022-3563.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/7700-3362-0922-7022-3563.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/7700-3362-0922-7022-3563.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/7700-3362-0922-7022-3563.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/7800-1501-0922-7127-3563.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/7800-1501-0922-7127-3563.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/7800-1501-0922-7127-3563.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/7800-1501-0922-7127-3563.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/7836-3125-0600-0526-2202.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/7836-3125-0600-0526-2202.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/7836-3125-0600-0526-2202.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/7836-3125-0600-0526-2202.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/8135-1728-8500-0511-3296.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/8135-1728-8500-0511-3296.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/8135-1728-8500-0511-3296.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/8135-1728-8500-0511-3296.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9036-0824-3500-0420-8222.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9036-0824-3500-0420-8222.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9036-0824-3500-0420-8222.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9036-0824-3500-0420-8222.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9285-3062-0205-7766-7200.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9285-3062-0205-7766-7200.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9285-3062-0205-7766-7200.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9285-3062-0205-7766-7200.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9370-3060-1205-3546-4204.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9370-3060-1205-3546-4204.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9370-3060-1205-3546-4204.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9370-3060-1205-3546-4204.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9380-2957-7490-2595-3141.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9380-2957-7490-2595-3141.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9380-2957-7490-2595-3141.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9380-2957-7490-2595-3141.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9390-2722-3520-2105-8715.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9390-2722-3520-2105-8715.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9390-2722-3520-2105-8715.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9390-2722-3520-2105-8715.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9418-3062-8205-3566-7200.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9418-3062-8205-3566-7200.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9418-3062-8205-3566-7200.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9418-3062-8205-3566-7200.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9421-3045-3205-1646-6200.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9421-3045-3205-1646-6200.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9421-3045-3205-1646-6200.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9421-3045-3205-1646-6200.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9501-3059-8202-7356-0204.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9501-3059-8202-7356-0204.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9501-3059-8202-7356-0204.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9501-3059-8202-7356-0204.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9796-3058-6205-0346-9200.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9796-3058-6205-0346-9200.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9796-3058-6205-0346-9200.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9796-3058-6205-0346-9200.json
diff --git a/domain/sap10_calculator/rdsap/tests/fixtures/golden/9836-7525-9500-0575-1202.json b/tests/domain/sap10_calculator/rdsap/fixtures/golden/9836-7525-9500-0575-1202.json
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/fixtures/golden/9836-7525-9500-0575-1202.json
rename to tests/domain/sap10_calculator/rdsap/fixtures/golden/9836-7525-9500-0575-1202.json
diff --git a/domain/sap10_calculator/rdsap/tests/test_cert_to_inputs.py b/tests/domain/sap10_calculator/rdsap/test_cert_to_inputs.py
similarity index 99%
rename from domain/sap10_calculator/rdsap/tests/test_cert_to_inputs.py
rename to tests/domain/sap10_calculator/rdsap/test_cert_to_inputs.py
index d8e448ad..f086cd36 100644
--- a/domain/sap10_calculator/rdsap/tests/test_cert_to_inputs.py
+++ b/tests/domain/sap10_calculator/rdsap/test_cert_to_inputs.py
@@ -64,7 +64,7 @@ from domain.sap10_calculator.rdsap.cert_to_inputs import (
     ventilation_from_cert,
 )
 from domain.sap10_calculator.tables.pcdb import GasOilBoilerRecord, gas_oil_boiler_record
-from domain.sap10_calculator.worksheet.tests import _elmhurst_worksheet_000477 as _w000477
+from tests.domain.sap10_calculator.worksheet import _elmhurst_worksheet_000477 as _w000477
 from domain.sap10_calculator.worksheet.water_heating import (
     combi_loss_monthly_kwh_table_3b_row_1_instantaneous,
     combi_loss_monthly_kwh_table_3c_two_profile_instantaneous,
@@ -3605,9 +3605,9 @@ def test_air_source_heat_pump_pcdb_104568_derives_apm_efficiencies_per_sap_app_n
     )
 
     doc = json.loads(
-        Path(
-            "/workspaces/model/domain/sap10_calculator/rdsap/tests/"
-            "fixtures/golden/0380-2471-3250-2596-8761.json"
+        (
+            Path(__file__).parent
+            / "fixtures" / "golden" / "0380-2471-3250-2596-8761.json"
         ).read_text()
     )
     epc = EpcPropertyDataMapper.from_api_response(doc)
@@ -3744,7 +3744,7 @@ def test_table_4c_no_boiler_interlock_applies_minus_5_dhw_adjustment_when_cylind
     # Arrange — use the real cert 000565 fixture (Elmhurst extractor +
     # mapper) so the (62)m demand cascade is the worksheet-pinned
     # tuple and only the (217)m efficiency step is under test.
-    from domain.sap10_calculator.worksheet.tests._elmhurst_worksheet_000565 import (
+    from tests.domain.sap10_calculator.worksheet._elmhurst_worksheet_000565 import (
         build_epc as build_cert_000565,
     )
     from domain.sap10_calculator.calculator import calculate_sap_from_inputs
@@ -4561,7 +4561,7 @@ def test_lighting_co2_factor_blends_table_12a_grid_2_with_table_12d_dual_rate_on
     """
     # Arrange — mapper-driven cohort fixture (Dual meter / TEN_HOUR
     # tariff, heat-pump main).
-    from domain.sap10_calculator.worksheet.tests import (
+    from tests.domain.sap10_calculator.worksheet import (
         _elmhurst_worksheet_000565 as _w000565,
     )
     epc = _w000565.build_epc()
@@ -4609,7 +4609,7 @@ def test_rdsap_10_table_32_prices_charge_mains_gas_hot_water_at_3p48_per_kwh() -
     """
     # Arrange — mapper-driven cohort fixture (Summary_000565 → cert_to_
     # inputs), Dual meter / mains gas DHW.
-    from domain.sap10_calculator.worksheet.tests import (
+    from tests.domain.sap10_calculator.worksheet import (
         _elmhurst_worksheet_000565 as _w000565,
     )
     epc = _w000565.build_epc()
diff --git a/domain/sap10_calculator/rdsap/tests/test_golden_fixtures.py b/tests/domain/sap10_calculator/rdsap/test_golden_fixtures.py
similarity index 100%
rename from domain/sap10_calculator/rdsap/tests/test_golden_fixtures.py
rename to tests/domain/sap10_calculator/rdsap/test_golden_fixtures.py
diff --git a/domain/sap10_calculator/tests/test_bre_worked_examples.py b/tests/domain/sap10_calculator/test_bre_worked_examples.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_bre_worked_examples.py
rename to tests/domain/sap10_calculator/test_bre_worked_examples.py
diff --git a/domain/sap10_calculator/tests/test_calculator.py b/tests/domain/sap10_calculator/test_calculator.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_calculator.py
rename to tests/domain/sap10_calculator/test_calculator.py
diff --git a/domain/sap10_calculator/tests/test_pcdb_etl.py b/tests/domain/sap10_calculator/test_pcdb_etl.py
similarity index 99%
rename from domain/sap10_calculator/tests/test_pcdb_etl.py
rename to tests/domain/sap10_calculator/test_pcdb_etl.py
index 13770f83..62ad46d6 100644
--- a/domain/sap10_calculator/tests/test_pcdb_etl.py
+++ b/tests/domain/sap10_calculator/test_pcdb_etl.py
@@ -24,7 +24,8 @@ from domain.sap10_calculator.tables.pcdb.parser import (
 
 
 _PCDB_DAT_PATH: Path = (
-    Path(__file__).resolve().parents[1] / "tables" / "pcdb" / "data" / "pcdb10.dat"
+    Path(__file__).resolve().parents[3]
+    / "domain" / "sap10_calculator" / "tables" / "pcdb" / "data" / "pcdb10.dat"
 )
 
 
diff --git a/domain/sap10_calculator/tests/test_pcdb_lookup.py b/tests/domain/sap10_calculator/test_pcdb_lookup.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_pcdb_lookup.py
rename to tests/domain/sap10_calculator/test_pcdb_lookup.py
diff --git a/domain/sap10_calculator/tests/test_pcdb_table_322_lookup.py b/tests/domain/sap10_calculator/test_pcdb_table_322_lookup.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_pcdb_table_322_lookup.py
rename to tests/domain/sap10_calculator/test_pcdb_table_322_lookup.py
diff --git a/domain/sap10_calculator/tests/test_pcdb_table_329_lookup.py b/tests/domain/sap10_calculator/test_pcdb_table_329_lookup.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_pcdb_table_329_lookup.py
rename to tests/domain/sap10_calculator/test_pcdb_table_329_lookup.py
diff --git a/domain/sap10_calculator/tests/test_pcdb_table_362_lookup.py b/tests/domain/sap10_calculator/test_pcdb_table_362_lookup.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_pcdb_table_362_lookup.py
rename to tests/domain/sap10_calculator/test_pcdb_table_362_lookup.py
diff --git a/domain/sap10_calculator/tests/test_postcode_weather.py b/tests/domain/sap10_calculator/test_postcode_weather.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_postcode_weather.py
rename to tests/domain/sap10_calculator/test_postcode_weather.py
diff --git a/domain/sap10_calculator/tests/test_table_12.py b/tests/domain/sap10_calculator/test_table_12.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_table_12.py
rename to tests/domain/sap10_calculator/test_table_12.py
diff --git a/domain/sap10_calculator/tests/test_table_12a.py b/tests/domain/sap10_calculator/test_table_12a.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_table_12a.py
rename to tests/domain/sap10_calculator/test_table_12a.py
diff --git a/domain/sap10_calculator/tests/test_table_32.py b/tests/domain/sap10_calculator/test_table_32.py
similarity index 100%
rename from domain/sap10_calculator/tests/test_table_32.py
rename to tests/domain/sap10_calculator/test_table_32.py
diff --git a/domain/sap10_calculator/validation/tests/__init__.py b/tests/domain/sap10_calculator/validation/__init__.py
similarity index 100%
rename from domain/sap10_calculator/validation/tests/__init__.py
rename to tests/domain/sap10_calculator/validation/__init__.py
diff --git a/domain/sap10_calculator/validation/tests/test_parity_report.py b/tests/domain/sap10_calculator/validation/test_parity_report.py
similarity index 100%
rename from domain/sap10_calculator/validation/tests/test_parity_report.py
rename to tests/domain/sap10_calculator/validation/test_parity_report.py
diff --git a/domain/sap10_calculator/worksheet/tests/__init__.py b/tests/domain/sap10_calculator/worksheet/__init__.py
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/__init__.py
rename to tests/domain/sap10_calculator/worksheet/__init__.py
diff --git a/domain/sap10_calculator/worksheet/tests/_elmhurst_fixtures.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_fixtures.py
similarity index 97%
rename from domain/sap10_calculator/worksheet/tests/_elmhurst_fixtures.py
rename to tests/domain/sap10_calculator/worksheet/_elmhurst_fixtures.py
index 51b48950..18eed5ef 100644
--- a/domain/sap10_calculator/worksheet/tests/_elmhurst_fixtures.py
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_fixtures.py
@@ -24,7 +24,7 @@ SECTION_8C_INTERMITTENCY_MONTHLY: tuple[float, ...] = (
     0.0, 0.0, 0.0, 0.0, 0.0, 0.25, 0.25, 0.25, 0.0, 0.0, 0.0, 0.0,
 )
 
-from domain.sap10_calculator.worksheet.tests import (
+from tests.domain.sap10_calculator.worksheet import (
     _elmhurst_worksheet_000474 as w000474,
     _elmhurst_worksheet_000477 as w000477,
     _elmhurst_worksheet_000480 as w000480,
diff --git a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000474.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000474.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000474.py
rename to tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000474.py
index c53c9625..1c7f4787 100644
--- a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000474.py
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000474.py
@@ -41,7 +41,7 @@ from domain.sap10_calculator.worksheet.solar_gains import RoofWindowInput, Roofl
 from domain.sap10_calculator.worksheet.ventilation import MechanicalVentilationKind
 from domain.sap10_calculator.worksheet.water_heating import TABLE_J1_TCOLD_FROM_MAINS_C
 
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (
     SECTION_8C_ALL_ZERO_MONTHLY,
     SECTION_8C_ETA_LOSS_ALL_ONE,
     SECTION_8C_INTERMITTENCY_MONTHLY,
diff --git a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000477.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000477.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000477.py
rename to tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000477.py
index 95a5d25f..a73f047b 100644
--- a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000477.py
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000477.py
@@ -39,7 +39,7 @@ from domain.sap10_calculator.worksheet.solar_gains import RoofWindowInput, Roofl
 from domain.sap10_calculator.worksheet.ventilation import MechanicalVentilationKind
 from domain.sap10_calculator.worksheet.water_heating import TABLE_J1_TCOLD_FROM_MAINS_C
 
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (
     SECTION_8C_ALL_ZERO_MONTHLY,
     SECTION_8C_ETA_LOSS_ALL_ONE,
     SECTION_8C_INTERMITTENCY_MONTHLY,
diff --git a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000480.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000480.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000480.py
rename to tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000480.py
index bf0462df..145ef3d0 100644
--- a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000480.py
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000480.py
@@ -40,7 +40,7 @@ from domain.sap10_calculator.worksheet.solar_gains import RoofWindowInput, Roofl
 from domain.sap10_calculator.worksheet.ventilation import MechanicalVentilationKind
 from domain.sap10_calculator.worksheet.water_heating import TABLE_J1_TCOLD_FROM_MAINS_C
 
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (
     SECTION_8C_ALL_ZERO_MONTHLY,
     SECTION_8C_ETA_LOSS_ALL_ONE,
     SECTION_8C_INTERMITTENCY_MONTHLY,
diff --git a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000487.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000487.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000487.py
rename to tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000487.py
index 94644d25..a5cbe9b4 100644
--- a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000487.py
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000487.py
@@ -260,7 +260,7 @@ def build_epc() -> EpcPropertyData:
 # ============================================================================
 from domain.sap10_calculator.worksheet.ventilation import MechanicalVentilationKind
 
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (
     SECTION_8C_ALL_ZERO_MONTHLY,
     SECTION_8C_ETA_LOSS_ALL_ONE,
     SECTION_8C_INTERMITTENCY_MONTHLY,
diff --git a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000490.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000490.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000490.py
rename to tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000490.py
index 80980f7c..f06194a4 100644
--- a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000490.py
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000490.py
@@ -43,7 +43,7 @@ from domain.sap10_calculator.worksheet.solar_gains import RoofWindowInput, Roofl
 from domain.sap10_calculator.worksheet.ventilation import MechanicalVentilationKind
 from domain.sap10_calculator.worksheet.water_heating import TABLE_J1_TCOLD_FROM_MAINS_C
 
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (
     SECTION_8C_ALL_ZERO_MONTHLY,
     SECTION_8C_ETA_LOSS_ALL_ONE,
     SECTION_8C_INTERMITTENCY_MONTHLY,
diff --git a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000516.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000516.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000516.py
rename to tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000516.py
index 9444e226..c561b353 100644
--- a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000516.py
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000516.py
@@ -46,7 +46,7 @@ from domain.sap10_calculator.worksheet.solar_gains import Orientation, RoofWindo
 from domain.sap10_calculator.worksheet.ventilation import MechanicalVentilationKind
 from domain.sap10_calculator.worksheet.water_heating import TABLE_J1_TCOLD_FROM_MAINS_C
 
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (
     SECTION_8C_ALL_ZERO_MONTHLY,
     SECTION_8C_ETA_LOSS_ALL_ONE,
     SECTION_8C_INTERMITTENCY_MONTHLY,
diff --git a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000565.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000565.py
similarity index 97%
rename from domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000565.py
rename to tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000565.py
index 774b148c..d01f2465 100644
--- a/domain/sap10_calculator/worksheet/tests/_elmhurst_worksheet_000565.py
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000565.py
@@ -61,8 +61,8 @@ from datatypes.epc.domain.epc_property_data import EpcPropertyData
 from datatypes.epc.domain.mapper import EpcPropertyDataMapper
 
 
-# Repo root → backend fixtures. parents[0]=tests/, parents[1]=worksheet/,
-# parents[2]=sap10_calculator/, parents[3]=domain/, parents[4]=repo root.
+# Repo root → backend fixtures. parents[0]=worksheet/, parents[1]=sap10_calculator/,
+# parents[2]=domain/, parents[3]=tests/, parents[4]=repo root.
 _SUMMARY_PDF: Final[Path] = (
     Path(__file__).resolve().parents[4]
     / "backend" / "documents_parser" / "tests" / "fixtures"
diff --git a/domain/sap10_calculator/worksheet/tests/_xlsx_loader.py b/tests/domain/sap10_calculator/worksheet/_xlsx_loader.py
similarity index 73%
rename from domain/sap10_calculator/worksheet/tests/_xlsx_loader.py
rename to tests/domain/sap10_calculator/worksheet/_xlsx_loader.py
index 0c528080..ef8d2ea1 100644
--- a/domain/sap10_calculator/worksheet/tests/_xlsx_loader.py
+++ b/tests/domain/sap10_calculator/worksheet/_xlsx_loader.py
@@ -19,6 +19,7 @@ from pathlib import Path
 from typing import Any, Iterable
 
 import openpyxl
+import pytest
 
 _REPO_ROOT = Path(__file__).resolve().parents[4]
 WORKSHEET_XLSX_PATH = _REPO_ROOT / "2026-05-19-17-18 RdSap10Worksheet.xlsx"
@@ -36,5 +37,14 @@ def load_cells(sheet_name: str, cells: Iterable[str]) -> dict[str, Any]:
     last-computed result rather than the formula string. Cell refs use
     standard Excel notation, e.g. "Q23", "U25".
     """
+    if not WORKSHEET_XLSX_PATH.exists():
+        # The canonical worksheet xlsx is a gitignored dev reference
+        # (`.gitignore` `*.xlsx`), so it isn't available in CI. Tests that
+        # pin the calculator against it run locally only and skip cleanly
+        # when it's absent rather than erroring with FileNotFoundError.
+        pytest.skip(
+            f"reference worksheet not present ({WORKSHEET_XLSX_PATH.name}); "
+            "gitignored dev artifact — xlsx-pinned tests are local-only"
+        )
     sheet = _workbook()[sheet_name]
     return {ref: sheet[ref].value for ref in cells}
diff --git a/domain/sap10_calculator/worksheet/tests/fixtures/basement/0712-3058-2202-3816-8204.json b/tests/domain/sap10_calculator/worksheet/fixtures/basement/0712-3058-2202-3816-8204.json
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/fixtures/basement/0712-3058-2202-3816-8204.json
rename to tests/domain/sap10_calculator/worksheet/fixtures/basement/0712-3058-2202-3816-8204.json
diff --git a/domain/sap10_calculator/worksheet/tests/fixtures/rir/0636-6824-0100-0500-6222.json b/tests/domain/sap10_calculator/worksheet/fixtures/rir/0636-6824-0100-0500-6222.json
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/fixtures/rir/0636-6824-0100-0500-6222.json
rename to tests/domain/sap10_calculator/worksheet/fixtures/rir/0636-6824-0100-0500-6222.json
diff --git a/domain/sap10_calculator/worksheet/tests/fixtures/rir/0636-8125-6600-0416-2202.json b/tests/domain/sap10_calculator/worksheet/fixtures/rir/0636-8125-6600-0416-2202.json
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/fixtures/rir/0636-8125-6600-0416-2202.json
rename to tests/domain/sap10_calculator/worksheet/fixtures/rir/0636-8125-6600-0416-2202.json
diff --git a/domain/sap10_calculator/worksheet/tests/fixtures/rir/0782-3058-6209-9186-1200.json b/tests/domain/sap10_calculator/worksheet/fixtures/rir/0782-3058-6209-9186-1200.json
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/fixtures/rir/0782-3058-6209-9186-1200.json
rename to tests/domain/sap10_calculator/worksheet/fixtures/rir/0782-3058-6209-9186-1200.json
diff --git a/domain/sap10_calculator/worksheet/tests/test_appendix_h_solar.py b/tests/domain/sap10_calculator/worksheet/test_appendix_h_solar.py
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/test_appendix_h_solar.py
rename to tests/domain/sap10_calculator/worksheet/test_appendix_h_solar.py
diff --git a/domain/sap10_calculator/worksheet/tests/test_dimensions.py b/tests/domain/sap10_calculator/worksheet/test_dimensions.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_dimensions.py
rename to tests/domain/sap10_calculator/worksheet/test_dimensions.py
index 858c739e..0f37c536 100644
--- a/domain/sap10_calculator/worksheet/tests/test_dimensions.py
+++ b/tests/domain/sap10_calculator/worksheet/test_dimensions.py
@@ -27,7 +27,7 @@ from domain.sap10_ml.tests._fixtures import (
     make_minimal_sap10_epc,
 )
 from domain.sap10_calculator.worksheet.dimensions import Dimensions, dimensions_from_cert
-from domain.sap10_calculator.worksheet.tests._xlsx_loader import load_cells
+from tests.domain.sap10_calculator.worksheet._xlsx_loader import load_cells
 
 _RIR_FIXTURES_DIR = Path(__file__).parent / "fixtures" / "rir"
 
@@ -507,7 +507,7 @@ def test_all_rir_shapes_apply_section_1_2_45m_convention_uniformly(
 
 
 from types import ModuleType  # noqa: E402  (kept near the Elmhurst tests)
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (  # noqa: E402
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (  # noqa: E402
     ALL_FIXTURES as _ELMHURST_FIXTURES,
     fixture_id as _elmhurst_fixture_id,
 )
diff --git a/domain/sap10_calculator/worksheet/tests/test_e2e_elmhurst_sap_score.py b/tests/domain/sap10_calculator/worksheet/test_e2e_elmhurst_sap_score.py
similarity index 98%
rename from domain/sap10_calculator/worksheet/tests/test_e2e_elmhurst_sap_score.py
rename to tests/domain/sap10_calculator/worksheet/test_e2e_elmhurst_sap_score.py
index 3b385b60..69ad44ba 100644
--- a/domain/sap10_calculator/worksheet/tests/test_e2e_elmhurst_sap_score.py
+++ b/tests/domain/sap10_calculator/worksheet/test_e2e_elmhurst_sap_score.py
@@ -29,7 +29,7 @@ from domain.sap10_calculator.rdsap.cert_to_inputs import (
     cert_to_inputs,
     water_heating_section_from_cert,
 )
-from domain.sap10_calculator.worksheet.tests import (
+from tests.domain.sap10_calculator.worksheet import (
     _elmhurst_worksheet_000474 as _w000474,
     _elmhurst_worksheet_000477 as _w000477,
     _elmhurst_worksheet_000480 as _w000480,
@@ -38,7 +38,7 @@ from domain.sap10_calculator.worksheet.tests import (
     _elmhurst_worksheet_000516 as _w000516,
     _elmhurst_worksheet_000565 as _w000565,
 )
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (
     ALL_FIXTURES as _ELMHURST_FIXTURES,
     fixture_id as _elmhurst_fixture_id,
 )
diff --git a/domain/sap10_calculator/worksheet/tests/test_energy_requirements.py b/tests/domain/sap10_calculator/worksheet/test_energy_requirements.py
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/test_energy_requirements.py
rename to tests/domain/sap10_calculator/worksheet/test_energy_requirements.py
diff --git a/domain/sap10_calculator/worksheet/tests/test_fabric_energy_efficiency.py b/tests/domain/sap10_calculator/worksheet/test_fabric_energy_efficiency.py
similarity index 96%
rename from domain/sap10_calculator/worksheet/tests/test_fabric_energy_efficiency.py
rename to tests/domain/sap10_calculator/worksheet/test_fabric_energy_efficiency.py
index 33c0b834..279acfff 100644
--- a/domain/sap10_calculator/worksheet/tests/test_fabric_energy_efficiency.py
+++ b/tests/domain/sap10_calculator/worksheet/test_fabric_energy_efficiency.py
@@ -13,7 +13,7 @@ import pytest
 from domain.sap10_calculator.worksheet.fabric_energy_efficiency import (
     fabric_energy_efficiency_kwh_per_m2_yr,
 )
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import ALL_FIXTURES, fixture_id
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import ALL_FIXTURES, fixture_id
 
 
 def test_fabric_energy_efficiency_sums_heating_per_m2_and_cooling_per_m2() -> None:
diff --git a/domain/sap10_calculator/worksheet/tests/test_fuel_cost.py b/tests/domain/sap10_calculator/worksheet/test_fuel_cost.py
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/test_fuel_cost.py
rename to tests/domain/sap10_calculator/worksheet/test_fuel_cost.py
diff --git a/domain/sap10_calculator/worksheet/tests/test_heat_transmission.py b/tests/domain/sap10_calculator/worksheet/test_heat_transmission.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_heat_transmission.py
rename to tests/domain/sap10_calculator/worksheet/test_heat_transmission.py
index 3e2660b2..b9f54aae 100644
--- a/domain/sap10_calculator/worksheet/tests/test_heat_transmission.py
+++ b/tests/domain/sap10_calculator/worksheet/test_heat_transmission.py
@@ -1326,11 +1326,11 @@ def test_real_corpus_basement_cert_has_part_with_has_basement_true() -> None:
 
 
 from types import ModuleType  # noqa: E402
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (  # noqa: E402
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (  # noqa: E402
     ALL_FIXTURES as _ELMHURST_FIXTURES,
     fixture_id as _elmhurst_fixture_id,
 )
-from domain.sap10_calculator.worksheet.tests import (  # noqa: E402
+from tests.domain.sap10_calculator.worksheet import (  # noqa: E402
     _elmhurst_worksheet_000474 as _w000474,
     _elmhurst_worksheet_000490 as _w000490,
 )
diff --git a/domain/sap10_calculator/worksheet/tests/test_internal_gains.py b/tests/domain/sap10_calculator/worksheet/test_internal_gains.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_internal_gains.py
rename to tests/domain/sap10_calculator/worksheet/test_internal_gains.py
index c63eea1d..3c8c07a2 100644
--- a/domain/sap10_calculator/worksheet/tests/test_internal_gains.py
+++ b/tests/domain/sap10_calculator/worksheet/test_internal_gains.py
@@ -44,7 +44,7 @@ from datatypes.epc.domain.epc_property_data import (
     SapWindow,
 )
 from domain.sap10_ml.tests._fixtures import make_minimal_sap10_epc
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import ALL_FIXTURES, fixture_id
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import ALL_FIXTURES, fixture_id
 
 
 def test_metabolic_gains_are_60w_per_occupant_constant_across_months() -> None:
diff --git a/domain/sap10_calculator/worksheet/tests/test_mean_internal_temperature.py b/tests/domain/sap10_calculator/worksheet/test_mean_internal_temperature.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_mean_internal_temperature.py
rename to tests/domain/sap10_calculator/worksheet/test_mean_internal_temperature.py
index d209a1d1..a16d91a9 100644
--- a/domain/sap10_calculator/worksheet/tests/test_mean_internal_temperature.py
+++ b/tests/domain/sap10_calculator/worksheet/test_mean_internal_temperature.py
@@ -24,7 +24,7 @@ from domain.sap10_calculator.worksheet.mean_internal_temperature import (
     mean_internal_temperature_monthly,
     off_period_temperature_reduction_c,
 )
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import ALL_FIXTURES, fixture_id
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import ALL_FIXTURES, fixture_id
 
 
 # UK-average climate (region 0) external temperatures, Appendix U Table U1.
diff --git a/domain/sap10_calculator/worksheet/tests/test_mev.py b/tests/domain/sap10_calculator/worksheet/test_mev.py
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/test_mev.py
rename to tests/domain/sap10_calculator/worksheet/test_mev.py
diff --git a/domain/sap10_calculator/worksheet/tests/test_photovoltaic.py b/tests/domain/sap10_calculator/worksheet/test_photovoltaic.py
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/test_photovoltaic.py
rename to tests/domain/sap10_calculator/worksheet/test_photovoltaic.py
diff --git a/domain/sap10_calculator/worksheet/tests/test_rating.py b/tests/domain/sap10_calculator/worksheet/test_rating.py
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/test_rating.py
rename to tests/domain/sap10_calculator/worksheet/test_rating.py
diff --git a/domain/sap10_calculator/worksheet/tests/test_section_cascade_pins.py b/tests/domain/sap10_calculator/worksheet/test_section_cascade_pins.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_section_cascade_pins.py
rename to tests/domain/sap10_calculator/worksheet/test_section_cascade_pins.py
index 8121d7b9..b3480d2a 100644
--- a/domain/sap10_calculator/worksheet/tests/test_section_cascade_pins.py
+++ b/tests/domain/sap10_calculator/worksheet/test_section_cascade_pins.py
@@ -35,7 +35,7 @@ from domain.sap10_calculator.rdsap.cert_to_inputs import (
     water_heating_section_from_cert,
 )
 from domain.sap10_calculator.worksheet.dimensions import dimensions_from_cert
-from domain.sap10_calculator.worksheet.tests import (
+from tests.domain.sap10_calculator.worksheet import (
     _elmhurst_worksheet_000474 as _w000474,
     _elmhurst_worksheet_000477 as _w000477,
     _elmhurst_worksheet_000480 as _w000480,
diff --git a/domain/sap10_calculator/worksheet/tests/test_solar_gains.py b/tests/domain/sap10_calculator/worksheet/test_solar_gains.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_solar_gains.py
rename to tests/domain/sap10_calculator/worksheet/test_solar_gains.py
index 3f368fa2..bb3ff89d 100644
--- a/domain/sap10_calculator/worksheet/tests/test_solar_gains.py
+++ b/tests/domain/sap10_calculator/worksheet/test_solar_gains.py
@@ -29,7 +29,7 @@ from domain.sap10_calculator.worksheet.solar_gains import (
     window_solar_gain_w,
     z_solar_for_overshading,
 )
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import ALL_FIXTURES, fixture_id
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import ALL_FIXTURES, fixture_id
 
 
 # Worksheet U985-0001-000490 reference (UK-avg weather, region 0):
diff --git a/domain/sap10_calculator/worksheet/tests/test_space_cooling.py b/tests/domain/sap10_calculator/worksheet/test_space_cooling.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_space_cooling.py
rename to tests/domain/sap10_calculator/worksheet/test_space_cooling.py
index 4f0d8a2f..28343680 100644
--- a/domain/sap10_calculator/worksheet/tests/test_space_cooling.py
+++ b/tests/domain/sap10_calculator/worksheet/test_space_cooling.py
@@ -14,7 +14,7 @@ from domain.sap10_calculator.worksheet.space_cooling import (
     space_cooling_monthly_kwh,
     utilisation_factor_loss,
 )
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import ALL_FIXTURES, fixture_id
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import ALL_FIXTURES, fixture_id
 
 
 _FULLY_INACTIVE_GAINS_WINTER_TE_C: float = -10.0
diff --git a/domain/sap10_calculator/worksheet/tests/test_space_heating.py b/tests/domain/sap10_calculator/worksheet/test_space_heating.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_space_heating.py
rename to tests/domain/sap10_calculator/worksheet/test_space_heating.py
index f279cbb4..d69a6114 100644
--- a/domain/sap10_calculator/worksheet/tests/test_space_heating.py
+++ b/tests/domain/sap10_calculator/worksheet/test_space_heating.py
@@ -17,7 +17,7 @@ from domain.sap10_calculator.worksheet.space_heating import (
     monthly_heat_requirement_kwh,
     space_heating_monthly_kwh,
 )
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import ALL_FIXTURES, fixture_id
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import ALL_FIXTURES, fixture_id
 
 
 _UK_AVG_EXT_TEMP_C: tuple[float, ...] = tuple(
diff --git a/domain/sap10_calculator/worksheet/tests/test_utilisation_factor.py b/tests/domain/sap10_calculator/worksheet/test_utilisation_factor.py
similarity index 100%
rename from domain/sap10_calculator/worksheet/tests/test_utilisation_factor.py
rename to tests/domain/sap10_calculator/worksheet/test_utilisation_factor.py
diff --git a/domain/sap10_calculator/worksheet/tests/test_ventilation.py b/tests/domain/sap10_calculator/worksheet/test_ventilation.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_ventilation.py
rename to tests/domain/sap10_calculator/worksheet/test_ventilation.py
index f307b354..ba0ee229 100644
--- a/domain/sap10_calculator/worksheet/tests/test_ventilation.py
+++ b/tests/domain/sap10_calculator/worksheet/test_ventilation.py
@@ -12,7 +12,7 @@ Canonical worked example: `2026-05-19-17-18 RdSap10Worksheet.xlsx`,
 
 import pytest
 
-from domain.sap10_calculator.worksheet.tests._xlsx_loader import load_cells
+from tests.domain.sap10_calculator.worksheet._xlsx_loader import load_cells
 from domain.sap10_calculator.worksheet.ventilation import (
     MechanicalVentilationKind,
     TABLE_U2_NON_REGIONAL_WIND_SPEED_M_S,
@@ -461,7 +461,7 @@ def test_excel_worksheet_conformance_section_2_lines_6a_to_25m() -> None:
 
 
 from types import ModuleType  # noqa: E402
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import (  # noqa: E402
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (  # noqa: E402
     ALL_FIXTURES as _ELMHURST_FIXTURES,
     fixture_id as _elmhurst_fixture_id,
 )
diff --git a/domain/sap10_calculator/worksheet/tests/test_water_heating.py b/tests/domain/sap10_calculator/worksheet/test_water_heating.py
similarity index 99%
rename from domain/sap10_calculator/worksheet/tests/test_water_heating.py
rename to tests/domain/sap10_calculator/worksheet/test_water_heating.py
index bc3cdcdf..e8e85b1e 100644
--- a/domain/sap10_calculator/worksheet/tests/test_water_heating.py
+++ b/tests/domain/sap10_calculator/worksheet/test_water_heating.py
@@ -12,13 +12,13 @@ from types import ModuleType
 
 import pytest
 
-from domain.sap10_calculator.worksheet.tests import (
+from tests.domain.sap10_calculator.worksheet import (
     _elmhurst_worksheet_000474 as _w000474,
     _elmhurst_worksheet_000477 as _w000477,
     _elmhurst_worksheet_000490 as _w000490,
 )
-from domain.sap10_calculator.worksheet.tests._elmhurst_fixtures import ALL_FIXTURES, fixture_id
-from domain.sap10_calculator.worksheet.tests._xlsx_loader import load_cells
+from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import ALL_FIXTURES, fixture_id
+from tests.domain.sap10_calculator.worksheet._xlsx_loader import load_cells
 from domain.sap10_calculator.worksheet.water_heating import (
     TABLE_J1_TCOLD_FROM_MAINS_C,
     annual_average_hot_water_l_per_day,
@@ -678,7 +678,7 @@ def test_000490_cert_to_inputs_hot_water_kwh_closes_via_equation_d1() -> None:
     2851 (target ±2%)."""
     # Arrange
     from domain.sap10_calculator.rdsap.cert_to_inputs import cert_to_inputs
-    from domain.sap10_calculator.worksheet.tests import _elmhurst_worksheet_000490 as _w000490
+    from tests.domain.sap10_calculator.worksheet import _elmhurst_worksheet_000490 as _w000490
 
     epc = _w000490.build_epc()