Add subprocess in test

tests/unit/test_simulation.py

@@ -2,7 +2,10 @@
 import numpy as np
 import pandas as pd
 import os
+import subprocess
+import sys
 import unittest
+import uuid
 
 
 class TestSimulation(unittest.TestCase):
@@ -267,17 +270,23 @@ def test_save_load(self):
 
     def test_load_param(self):
         # Test load_sim for parameters imports
-        pkl_obj = pybamm.load_sim(
-            os.path.join(
-                "tests", "unit", "test_parameters", "data", "test_load_param.p"
-            )
-        )
+        filename = f"{uuid.uuid4()}.p"
+        save_sim = f"import pybamm; model = pybamm.lithium_ion.SPM(); params = pybamm.ParameterValues(chemistry=pybamm.parameter_sets.Chen2020); sim = pybamm.Simulation(model, parameter_values=params); sim.solve([0, 3600]); sim.save('{filename}')"  # noqa
+        subprocess.run([sys.executable, "-c", save_sim])
+
+        try:
+            pkl_obj = pybamm.load_sim(os.path.join(filename))
+        except Exception as excep:
+            os.remove(filename)
+            raise excep
+
         self.assertEqual(
             "graphite_LGM50_electrolyte_exchange_current_density_Chen2020",
             pkl_obj.parameter_values[
                 "Negative electrode exchange-current density [A.m-2]"
             ].__name__,
         )
+        os.remove(filename)
 
     def test_save_load_dae(self):
         model = pybamm.lead_acid.LOQS({"surface form": "algebraic"})
@@ -424,7 +433,6 @@ def test_battery_model_with_input_height(self):
 
 if __name__ == "__main__":
     print("Add -v for more debug output")
-    import sys
 
     if "-v" in sys.argv:
         debug = True