diff --git a/tests/unit/test_cost.py b/tests/unit/test_cost.py
index 3f2e1401..a89dc428 100644
--- a/tests/unit/test_cost.py
+++ b/tests/unit/test_cost.py
@@ -19,7 +19,7 @@ def __init__(self, problem, sigma0):
     @pytest.fixture
     def model(self, ground_truth):
         model = pybop.lithium_ion.SPM()
-        model._parameter_set["Negative electrode active material volume fraction"] = (
+        model.parameter_set["Negative electrode active material volume fraction"] = (
             ground_truth
         )
         return model
@@ -297,7 +297,7 @@ def test_design_costs(self, cost_class, design_problem):
     @pytest.fixture
     def noisy_problem(self, ground_truth, parameters, experiment):
         model = pybop.lithium_ion.SPM()
-        model._parameter_set["Negative electrode active material volume fraction"] = (
+        model.parameter_set["Negative electrode active material volume fraction"] = (
             ground_truth
         )
         sol = model.predict(experiment=experiment)
diff --git a/tests/unit/test_models.py b/tests/unit/test_models.py
index b090f570..1e8673d2 100644
--- a/tests/unit/test_models.py
+++ b/tests/unit/test_models.py
@@ -192,18 +192,18 @@ def test_parameter_set_definition(self):
         # Test initilisation with different types of parameter set
         param_dict = {"Nominal cell capacity [A.h]": 5}
         model = pybop.BaseModel(parameter_set=None)
-        assert model._parameter_set is None
+        assert model.parameter_set is None
 
         model = pybop.BaseModel(parameter_set=param_dict)
         parameter_set = pybamm.ParameterValues(param_dict)
-        assert model._parameter_set == parameter_set
+        assert model.parameter_set == parameter_set
 
         model = pybop.BaseModel(parameter_set=parameter_set)
-        assert model._parameter_set == parameter_set
+        assert model.parameter_set == parameter_set
 
         pybop_parameter_set = pybop.ParameterSet(params_dict=param_dict)
         model = pybop.BaseModel(parameter_set=pybop_parameter_set)
-        assert model._parameter_set == parameter_set
+        assert model.parameter_set == parameter_set
 
     @pytest.mark.unit
     def test_rebuild_geometric_parameters(self):
@@ -348,14 +348,14 @@ def test_thevenin_model(self):
         )
 
         model.predict(initial_state=0.5, t_eval=np.arange(0, 10, 5))
-        assert model._parameter_set["Initial SoC"] == 0.5
+        assert model.parameter_set["Initial SoC"] == 0.5
 
         model.set_initial_state(parameter_set["Initial SoC"] / 2)
-        assert model._parameter_set["Initial SoC"] == parameter_set["Initial SoC"] / 2
+        assert model.parameter_set["Initial SoC"] == parameter_set["Initial SoC"] / 2
         model.set_initial_state(str(parameter_set["Lower voltage cut-off [V]"]) + "V")
-        np.testing.assert_allclose(model._parameter_set["Initial SoC"], 0.0, atol=1e-2)
+        np.testing.assert_allclose(model.parameter_set["Initial SoC"], 0.0, atol=1e-2)
         model.set_initial_state(str(parameter_set["Upper voltage cut-off [V]"]) + "V")
-        np.testing.assert_allclose(model._parameter_set["Initial SoC"], 1.0, atol=1e-2)
+        np.testing.assert_allclose(model.parameter_set["Initial SoC"], 1.0, atol=1e-2)
 
         with pytest.raises(ValueError, match="outside the voltage limits"):
             model.set_initial_state("-1.0V")
diff --git a/tests/unit/test_problem.py b/tests/unit/test_problem.py
index 24164c71..11f5a771 100644
--- a/tests/unit/test_problem.py
+++ b/tests/unit/test_problem.py
@@ -184,7 +184,7 @@ def test_design_problem(self, parameters, experiment, model):
 
         # Test init_soc from parameter_set
         model = pybop.empirical.Thevenin()
-        model._parameter_set["Initial SoC"] = 0.8
+        model.parameter_set["Initial SoC"] = 0.8
         problem = pybop.DesignProblem(model, pybop.Parameters(), experiment)
         assert problem.init_soc == 0.8