From 84aef797355146a2b5901b59adcfa6be3688fa95 Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Mon, 23 Feb 2026 13:35:31 +0000
Subject: [PATCH] Added tests for checking ventilation

---
 backend/engine/engine.py                      |  7 ++-
 .../optimiser/optimiser_functions.py          | 23 +++++++
 .../tests/test_optimiser_functions.py         | 60 +++++++++++++++++++
 3 files changed, 87 insertions(+), 3 deletions(-)

diff --git a/backend/engine/engine.py b/backend/engine/engine.py
index 6c6b0c70..dd0aebe4 100644
--- a/backend/engine/engine.py
+++ b/backend/engine/engine.py
@@ -1060,9 +1060,10 @@ async def model_engine(body: PlanTriggerRequest):
             # If a measure requiring ventilation is selected, and the property does not have ventilation, we enfore
             # its inclusion
 
-            needs_ventilation = any(
-                x in property_measure_types for x in assumptions.measures_needing_ventilation
-            ) and not p.has_ventilation and ventilation_included
+            needs_ventilation = optimiser_functions.check_needs_ventilation(
+                property_measure_types, assumptions.measures_needing_ventilation, p.has_ventilation,
+                ventilation_included
+            )
 
             if not measures_to_optimise:
                 # Nothing to do, we just reshape the recommendations
diff --git a/recommendations/optimiser/optimiser_functions.py b/recommendations/optimiser/optimiser_functions.py
index e916f0fd..c17cdf1e 100644
--- a/recommendations/optimiser/optimiser_functions.py
+++ b/recommendations/optimiser/optimiser_functions.py
@@ -398,3 +398,26 @@ def flatten_recommendations_with_defaults(property_id, recommendations, selected
 
     # Flatten the nested list of lists into a single list
     return [rec for recommendations_by_type in final_recommendations for rec in recommendations_by_type]
+
+
+def check_needs_ventilation(
+    property_measure_types: Set[str],
+    measures_needing_ventilation: List[str],
+    has_ventilation: bool,
+    ventilation_included: bool
+) -> bool:
+    """
+    Function to check if we need to include ventilation based on the measures selected and the property
+    features
+    :param property_measure_types: The set of measure types recommended for the property
+    :param measures_needing_ventilation: The set of measure types that require ventilation
+    :param has_ventilation: Whether the property currently has ventilation
+    :param ventilation_included: Whether ventilation is already included in the recommended measures
+    :return: Boolean indicating whether ventilation needs to be included in the recommendations
+
+    # TODO - none of the inputs of this function are well structured and so this is quite brittle - we should
+             consider refactoring to make this more robust
+    """
+    return any(
+        x in property_measure_types for x in measures_needing_ventilation
+    ) and not has_ventilation and ventilation_included
diff --git a/recommendations/tests/test_optimiser_functions.py b/recommendations/tests/test_optimiser_functions.py
index f0ca6dac..8f898970 100644
--- a/recommendations/tests/test_optimiser_functions.py
+++ b/recommendations/tests/test_optimiser_functions.py
@@ -510,3 +510,63 @@ class TestStrategicOptimiser:
         assert opt.strategy_used.value == "case_2_solve_max_gain_under_budget"
         assert opt.solution_cost == 7787.068
         assert opt.solution_gain == 28.8
+
+
+class TestCheckNeedsVentilation:
+
+    def measure_types_includes_ventilation_no_existing_ventilation(self):
+        property_measure_types = {'mechanical_ventilation', 'cavity_wall_insulation', 'suspended_floor_insulation',
+                                  'secondary_heating', 'loft_insulation', 'heating', 'low_energy_lighting'}
+
+        measures_needing_ventilation = ['internal_wall_insulation', 'external_wall_insulation',
+                                        'cavity_wall_insulation']
+
+        has_ventilation = False
+
+        ventilation_included = True
+
+        result = optimiser_functions.check_needs_ventilation(
+            property_measure_types, measures_needing_ventilation, has_ventilation,
+            ventilation_included
+        )
+
+        assert result == True
+
+    def measure_types_includes_ventilation_existing_ventilation(self):
+        property_measure_types = {'mechanical_ventilation', 'cavity_wall_insulation', 'suspended_floor_insulation',
+                                  'secondary_heating', 'loft_insulation', 'heating', 'low_energy_lighting'}
+
+        measures_needing_ventilation = ['internal_wall_insulation', 'external_wall_insulation',
+                                        'cavity_wall_insulation']
+
+        has_ventilation = True
+
+        ventilation_included = True
+
+        result = optimiser_functions.check_needs_ventilation(
+            property_measure_types, measures_needing_ventilation, has_ventilation,
+            ventilation_included
+        )
+
+        assert result == False
+
+    def measure_types_includes_ventilation_existing_ventilation(self):
+        property_measure_types_without_ventilation = {
+            'cavity_wall_insulation', 'suspended_floor_insulation',
+            'secondary_heating', 'loft_insulation', 'heating',
+            'low_energy_lighting'
+        }
+
+        measures_needing_ventilation = ['internal_wall_insulation', 'external_wall_insulation',
+                                        'cavity_wall_insulation']
+
+        has_ventilation = False
+
+        ventilation_included = True
+
+        result = optimiser_functions.check_needs_ventilation(
+            property_measure_types_without_ventilation, measures_needing_ventilation, has_ventilation,
+            ventilation_included
+        )
+
+        assert result == False