diff --git a/tests/domain/modelling/test_optimiser_goal_objective.py b/tests/domain/modelling/test_optimiser_goal_objective.py
index f64371cc4..acd14b3ec 100644
--- a/tests/domain/modelling/test_optimiser_goal_objective.py
+++ b/tests/domain/modelling/test_optimiser_goal_objective.py
@@ -16,46 +16,25 @@ from datatypes.epc.domain.epc_property_data import (
 )
 from domain.modelling.measure_type import MeasureType
 from domain.modelling.optimisation.optimiser import (
-    MeasureDependency,
     OptimisedPackage,
     ScoredOption,
     optimise_package,
+    optimise_package_fabric_first,
 )
-from domain.modelling.recommendation import Cost, MeasureOption
 from domain.modelling.scoring.package_scorer import Score
-from domain.modelling.simulation import (
-    BuildingPartOverlay,
-    EpcSimulation,
-    HeatingOverlay,
-    VentilationOverlay,
+from domain.modelling.simulation import BuildingPartOverlay, EpcSimulation
+from tests.domain.modelling._optimiser_fixtures import (
+    ASHP_OVERLAY,
+    BOILER_OVERLAY,
+    WALL_OVERLAY,
+    scored_option,
+    selected_types,
+    ventilation_dependency,
 )
 from tests.domain.sap10_calculator.worksheet._elmhurst_worksheet_000490 import (
     build_epc,
 )
 
-_WALL_OVERLAY = EpcSimulation(
-    building_parts={
-        BuildingPartIdentifier.MAIN: BuildingPartOverlay(wall_insulation_type=2)
-    }
-)
-_VENT_OVERLAY = EpcSimulation(
-    ventilation=VentilationOverlay(mechanical_ventilation_kind="EXTRACT_OR_PIV_OUTSIDE")
-)
-
-
-def _scored(
-    measure_type: str, *, gain: float, cost: float, overlay: EpcSimulation
-) -> ScoredOption:
-    return ScoredOption(
-        option=MeasureOption(
-            measure_type=MeasureType(measure_type),
-            description=measure_type,
-            overlay=overlay,
-            cost=Cost(total=cost, contingency_rate=0.0),
-        ),
-        sap_gain=gain,
-    )
-
 
 class _CarbonScorer:
     """A stub where the wall is a small carbon win (−20 kg/yr) and a large SAP
@@ -89,19 +68,10 @@ def test_dependency_signals_are_priced_in_the_objective_currency() -> None:
     # pricing the ventilation's −30 SAP would outweigh the wall's +20 signal
     # and the package would collapse to nothing.
     groups: list[list[ScoredOption]] = [
-        [_scored("cavity_wall_insulation", gain=20.0, cost=1000.0, overlay=_WALL_OVERLAY)],
+        [scored_option("cavity_wall_insulation", gain=20.0, cost=1000.0, overlay=WALL_OVERLAY)],
     ]
-    dependency = MeasureDependency(
-        triggers=frozenset({MeasureType.CAVITY_WALL_INSULATION}),
-        required=ScoredOption(
-            option=MeasureOption(
-                measure_type=MeasureType.MECHANICAL_VENTILATION,
-                description="mechanical_ventilation",
-                overlay=_VENT_OVERLAY,
-                cost=Cost(total=300.0, contingency_rate=0.0),
-            ),
-            sap_gain=0.0,
-        ),
+    dependency = ventilation_dependency(
+        cost=300.0, triggers=frozenset({MeasureType.CAVITY_WALL_INSULATION})
     )
 
     # Act — a Reducing-CO2 brief: maximise carbon reduction within budget.
@@ -117,22 +87,21 @@ def test_dependency_signals_are_priced_in_the_objective_currency() -> None:
 
     # Assert — the wall survives with its ventilation: the dependency is worth
     # 0 kg CO2, not −30 SAP, so the package is a net +20 kg saving.
-    assert {s.option.measure_type for s in package.selected} == {
+    assert selected_types(package.selected) == {
         "cavity_wall_insulation",
         "mechanical_ventilation",
     }
     assert abs(package.score.co2_kg_per_yr - 480.0) <= 1e-9
 
 
+# Internal wall insulation — a distinct fabric overlay so the fabric-first
+# phase-1 pick is unambiguous. No shared fixture (the shared WALL_OVERLAY is a
+# cavity fill, type 2); this is a solid-wall internal treatment, type 3.
 _IWI_OVERLAY = EpcSimulation(
     building_parts={
         BuildingPartIdentifier.MAIN: BuildingPartOverlay(wall_insulation_type=3)
     }
 )
-_BOILER_OVERLAY = EpcSimulation(heating=HeatingOverlay(sap_main_heating_code=201))
-_ASHP_OVERLAY = EpcSimulation(
-    heating=HeatingOverlay(main_heating_index_number=13000)
-)
 
 
 class _CarbonHeatingScorer:
@@ -166,15 +135,11 @@ def test_fabric_first_phase_two_rescores_in_the_objective_currency() -> None:
     # Arrange — a fabric-first Reducing-CO2 brief. Phase 1 commits the wall;
     # phase 2 must choose the heating on its post-fabric *carbon* worth, not
     # its SAP worth. Signals are supplied in kg CO2 saved (the caller's job).
-    from domain.modelling.optimisation.optimiser import (
-        optimise_package_fabric_first,
-    )
-
     groups: list[list[ScoredOption]] = [
-        [_scored("internal_wall_insulation", gain=10.0, cost=1000.0, overlay=_IWI_OVERLAY)],
+        [scored_option("internal_wall_insulation", gain=10.0, cost=1000.0, overlay=_IWI_OVERLAY)],
         [
-            _scored("gas_boiler_upgrade", gain=5.0, cost=2000.0, overlay=_BOILER_OVERLAY),
-            _scored("air_source_heat_pump", gain=50.0, cost=6000.0, overlay=_ASHP_OVERLAY),
+            scored_option("gas_boiler_upgrade", gain=5.0, cost=2000.0, overlay=BOILER_OVERLAY),
+            scored_option("air_source_heat_pump", gain=50.0, cost=6000.0, overlay=ASHP_OVERLAY),
         ],
     ]
 
@@ -190,7 +155,7 @@ def test_fabric_first_phase_two_rescores_in_the_objective_currency() -> None:
 
     # Assert — the wall plus the heat pump (−50 kg), not the SAP-favoured
     # boiler; the truthful package carbon is 500 − 10 − 50 = 440.
-    assert {s.option.measure_type for s in package.selected} == {
+    assert selected_types(package.selected) == {
         "internal_wall_insulation",
         "air_source_heat_pump",
     }