#1456 fix test

Author: valentinsulzer

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()