diff --git a/bionetgen/modelapi/model.py b/bionetgen/modelapi/model.py
index 0ef3e666..4e5c8c51 100644
--- a/bionetgen/modelapi/model.py
+++ b/bionetgen/modelapi/model.py
@@ -1,4 +1,4 @@
-import copy, tempfile, shutil
+import copy, tempfile, shutil, os
 
 from bionetgen.main import BioNetGen
 from bionetgen.core.exc import BNGModelError
@@ -489,7 +489,7 @@ def setup_simulator(self, sim_type="libRR"):
             # with windows
             try:
                 tmp_folder = tempfile.mkdtemp()
-                sbml_name = f"{self.model_name}_sbml.xml"
+                sbml_name = os.path.join(tmp_folder, f"{self.model_name}_sbml.xml")
                 # write the sbml
                 with open(sbml_name, "w+") as f:
                     if not (
@@ -510,7 +510,10 @@ def setup_simulator(self, sim_type="libRR"):
                 selections = ["time"] + [obs for obs in self.observables]
                 self.simulator.simulator.timeCourseSelections = selections
             finally:
-                shutil.rmtree(tmp_folder)
+                try:
+                    shutil.rmtree(tmp_folder)
+                except Exception:
+                    pass
             self.actions = curr_actions
         elif sim_type == "cpy":
             # get the simulator
diff --git a/tests/test_csimulator.py b/tests/test_csimulator.py
index ebc5ee10..ba674cbf 100644
--- a/tests/test_csimulator.py
+++ b/tests/test_csimulator.py
@@ -60,11 +60,12 @@ def __init__(self):
 
     csim.model = MockModel()
 
-    with unittest.mock.patch(
-        "os.path.abspath", side_effect=lambda x: x
-    ), unittest.mock.patch(
-        "bionetgen.simulator.csimulator.CSimWrapper"
-    ) as mock_wrapper:
+    with (
+        unittest.mock.patch("os.path.abspath", side_effect=lambda x: x),
+        unittest.mock.patch(
+            "bionetgen.simulator.csimulator.CSimWrapper"
+        ) as mock_wrapper,
+    ):
         csim.simulator = "dummy_lib_file"
         mock_wrapper.assert_called_once()
         args, kwargs = mock_wrapper.call_args
@@ -131,3 +132,52 @@ def __init__(self):
     mock_wrapper.simulate.assert_called_once_with(1, 5, 4)
 
     assert res == ("timepoints", "obs_all", "spcs_all")
+
+
+def test_simulator_setter_success():
+    # Bypass init
+    sim = CSimulator.__new__(CSimulator)
+    sim.model = unittest.mock.Mock()
+
+    # Setup mock parameters and species
+    param_mock = unittest.mock.Mock()
+    param_mock.expr = "1.5"
+
+    param_invalid = unittest.mock.Mock()
+    param_invalid.expr = "not_a_float"
+
+    sim.model.parameters = {
+        "param1": param_mock,
+        "_ignored": unittest.mock.Mock(),
+        "param2": param_invalid,
+    }
+    sim.model.species = {"spec1": unittest.mock.Mock(), "spec2": unittest.mock.Mock()}
+
+    with unittest.mock.patch(
+        "bionetgen.simulator.csimulator.CSimWrapper"
+    ) as mock_wrapper:
+        sim.simulator = "dummy_lib"
+
+        # Check that CSimWrapper is instantiated correctly
+        mock_wrapper.assert_called_once()
+        args, kwargs = mock_wrapper.call_args
+        assert "dummy_lib" in args[0]
+        assert kwargs["num_params"] == 1  # only param1 is valid and not ignored
+        assert kwargs["num_spec_init"] == 2  # 2 species
+
+        # Check property getter
+        assert sim.simulator == mock_wrapper.return_value
+
+
+def test_simulator_setter_compile_error():
+    sim = CSimulator.__new__(CSimulator)
+    sim.model = unittest.mock.Mock()
+    sim.model.parameters = {}
+    sim.model.species = {}
+
+    with unittest.mock.patch(
+        "bionetgen.simulator.csimulator.CSimWrapper",
+        side_effect=Exception("Wrapper failed"),
+    ):
+        with pytest.raises(BNGCompileError):
+            sim.simulator = "dummy_lib"