diff --git a/tests/unit/test_models/test_submodels/test_electrolyte_diffusion/test_constant_concentration.py b/tests/unit/test_models/test_submodels/test_electrolyte_diffusion/test_constant_concentration.py
index 1d2c7898e6..877546e3f5 100644
--- a/tests/unit/test_models/test_submodels/test_electrolyte_diffusion/test_constant_concentration.py
+++ b/tests/unit/test_models/test_submodels/test_electrolyte_diffusion/test_constant_concentration.py
@@ -11,7 +11,13 @@ class TestConstantConcentration(unittest.TestCase):
     def test_public_functions(self):
         param = pybamm.LithiumIonParameters()
         a = pybamm.Scalar(0)
-        variables = {"Porosity": a, "Electrolyte concentration": a}
+        variables = {
+            "Porosity": a,
+            "Negative electrode porosity": a,
+            "Separator porosity": a,
+            "Positive electrode porosity": a,
+            "Electrolyte concentration": a,
+        }
         submodel = pybamm.electrolyte_diffusion.ConstantConcentration(param)
         std_tests = tests.StandardSubModelTests(submodel, variables)
         std_tests.test_all()