diff --git a/backend/categorisation/tests/test_prioritised_plan_selected.py b/backend/categorisation/tests/test_prioritised_plan_selected.py
index eb41194c..5424dd5e 100644
--- a/backend/categorisation/tests/test_prioritised_plan_selected.py
+++ b/backend/categorisation/tests/test_prioritised_plan_selected.py
@@ -15,67 +15,73 @@ def created_at_datetime() -> datetime:
     return datetime.now()
 
 
-@pytest.fixture
-def identical_plan_record(created_at_datetime: datetime, default: bool) -> PlanRecord:
+def make_plan_record(
+    created_at: datetime, default: bool, cost_of_works: float = 500.0
+) -> PlanRecord:
     return PlanRecord(
         property_id=1,
         portfolio_id=1,
-        created_at=created_at_datetime,
+        created_at=created_at,
         is_default=default,
         post_epc_rating=Epc.C,
-        cost_of_works=500.0,
+        cost_of_works=cost_of_works,
     )
 
 
-def make_plan_record(created_at_datetime: datetime, default: bool) -> PlanRecord:
-    return PlanRecord(
-        property_id=1,
-        portfolio_id=1,
-        created_at=created_at_datetime,
-        is_default=default,
-        post_epc_rating=Epc.C,
-        cost_of_works=500.0,
+def make_scenario(name: str, created_at: datetime, is_default: bool) -> Scenario:
+    record = ScenarioRecord(
+        name=name,
+        created_at=created_at,
+        housing_type="",
+        goal=PortfolioGoal.INCREASING_EPC,
+        goal_value="C",
+        trigger_file_path="",
+        multi_plan=False,
+        is_default=is_default,
+    )
+    return Scenario(record=record, id=1 if is_default else 2)
+
+
+def make_plan(
+    created_at: datetime, default: bool, cost_of_works: float = 500.0, name: str = ""
+) -> Plan:
+    scenario = make_scenario(name, created_at, default)
+    plan_id = 1 if default else 2
+    return Plan(
+        record=make_plan_record(created_at, default, cost_of_works),
+        scenario=scenario,
+        id=plan_id,
     )
 
 
 def test_prioritised_plan_selected(created_at_datetime: datetime) -> None:
     # arrange
-    epc_c_scenario_record = ScenarioRecord(
-        name="EPC C",
-        created_at=created_at_datetime,
-        housing_type="",
-        goal=PortfolioGoal.INCREASING_EPC,
-        goal_value="C",
-        trigger_file_path="",
-        multi_plan=False,
-        is_default=True,
-    )
-    epc_c_scenario = Scenario(record=epc_c_scenario_record, id=1)
-    epc_c_plan = Plan(
-        record=make_plan_record(created_at_datetime, True),
-        scenario=epc_c_scenario,
-        id=1,
-    )
-
-    minor_works_scenario_record = ScenarioRecord(
-        name="EPC C - Minor Works",
-        created_at=created_at_datetime,
-        housing_type="",
-        goal=PortfolioGoal.INCREASING_EPC,
-        goal_value="C",
-        trigger_file_path="",
-        multi_plan=False,
-        is_default=False,
-    )
-    minor_works_scenario = Scenario(record=minor_works_scenario_record, id=2)
-    minor_works_plan = Plan(
-        record=make_plan_record(created_at_datetime, False),
-        scenario=minor_works_scenario,
-        id=2,
-    )
-
+    epc_c_plan = make_plan(created_at_datetime, True, name="EPC C")
+    minor_works_plan = make_plan(created_at_datetime, False, name="EPC C - Minor Works")
     plan_priority_order: List[int] = [2, 1]
-
+    expected_default_plan_id = 2
+
+    # act
+    actual_default_plan = choose_cheapest_relevant_plan(
+        plans=[epc_c_plan, minor_works_plan],
+        plan_priority_order=plan_priority_order,
+    )
+
+    # assert
+    assert actual_default_plan.id == expected_default_plan_id
+
+
+def test_cheapest_plan_returned_if_not_in_priority_list(
+    created_at_datetime: datetime,
+) -> None:
+    # arrange
+    epc_c_plan = make_plan(
+        created_at_datetime, True, cost_of_works=1000.0, name="EPC C"
+    )
+    minor_works_plan = make_plan(
+        created_at_datetime, False, cost_of_works=100.0, name="EPC C - Minor Works"
+    )
+    plan_priority_order: List[int] = [1, 3]
     expected_default_plan_id = 2
 
     # act