diff --git a/recommendations/Costs.py b/recommendations/Costs.py
index d14b5f33..1fb1114d 100644
--- a/recommendations/Costs.py
+++ b/recommendations/Costs.py
@@ -122,16 +122,6 @@ class Costs:
 
         :return: A dictionary containing detailed cost breakdown.
         """
-        # Cost per m2
-        # material = {
-        #     "description": "cwi",
-        #     "depth": 75,
-        #     "thermal_conductivity": 0.037,
-        #     "prime_cost": 5.17,
-        #     "material_cost": 5.62,
-        #     "labour_cost": 1.125,
-        #     "labour_hours": 0.065
-        # }
 
         material_cost_per_m2 = material["material_cost"]
 
diff --git a/recommendations/tests/test_costs.py b/recommendations/tests/test_costs.py
index e69de29b..8ca12e0b 100644
--- a/recommendations/tests/test_costs.py
+++ b/recommendations/tests/test_costs.py
@@ -0,0 +1,33 @@
+from recommendations.Costs import Costs
+from unittest.mock import Mock
+
+
+class TestCosts:
+
+    def test_cavity_wall_insulation(self):
+        mock_property = Mock()
+        mock_property.data = {
+            "county": "Northamptonshire"
+        }
+
+        costs = Costs(mock_property)
+
+        cwi_material = {
+            "description": "cwi",
+            "depth": 75,
+            "thermal_conductivity": 0.037,
+            "prime_cost": 5.17,
+            "material_cost": 5.62,
+            "labour_cost": 1.125,
+            "labour_hours": 0.065
+        }
+
+        cwi_results = costs.cavity_wall_insulation(
+            wall_area=95.9104281347967,
+            material=cwi_material,
+        )
+
+        assert cwi_results == {'total': 1027.0280465530302, 'subtotal': 855.8567054608585, 'vat': 171.1713410921717,
+                               'contingency': 63.396792997100626, 'preliminaries': 63.396792997100626,
+                               'material': 539.0166061175574, 'profit': 95.09518949565093,
+                               'labour_hours': 6.234177828761786}