diff --git a/tests/describers/test_m3gnet.py b/tests/describers/test_m3gnet.py
index 657bf761..eb695926 100644
--- a/tests/describers/test_m3gnet.py
+++ b/tests/describers/test_m3gnet.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import numpy as np
+import pytest
 import unittest
 
 from pymatgen.core import Lattice, Structure
@@ -13,23 +14,29 @@
 from maml.describers import M3GNetStructure, M3GNetSite
 
 
-@unittest.skipIf(M3GNet is None, "M3GNet package is required")
+@unittest.skipIf(M3GNet is None, "M3GNet package is required.")
 class M3GNetTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         cls.s = Structure.from_spacegroup(
             "Fm-3m", Lattice.cubic(5.69169), ["Na", "Cl"], [[0, 0, 0], [0, 0, 0.5]]
         )
-        cls.m3gnet_struct = M3GNetStructure()
-        cls.m3gnet_site = M3GNetSite(feature_batch="pandas_concat")
 
     def test_m3gnet_site_transform(self):
-        atom_features2 = self.m3gnet_site.transform([self.s] * 2)
-        self.assertListEqual(list(np.array(atom_features2).shape), [16, 64])
+        atom_feat_2s = M3GNetSite(feature_batch="pandas_concat").transform([self.s] * 2)
+        self.assertListEqual(list(np.array(atom_feat_2s).shape), [16, 64])
+        with pytest.raises(ValueError, match="Invalid output_layers"):
+            M3GNetSite(output_layers=["whatever"])
+        atom_feat_2s_2l = M3GNetSite(
+            output_layers=["embedding", "gc_3"], feature_batch="pandas_concat"
+        ).transform([self.s] * 2)
+        self.assertListEqual(list(np.array(atom_feat_2s_2l).shape), [16, 128])
+        atom_feat_dict = M3GNetSite(return_type=dict).transform_one(self.s)
+        assert type(atom_feat_dict) == dict
 
     def test_m3gnet_structure_transform(self):
-        struct_feature2 = self.m3gnet_struct.transform([self.s] * 2)
-        self.assertListEqual(list(np.array(struct_feature2).shape), [2, 128])
+        struct_feat_2s = M3GNetStructure().transform([self.s] * 2)
+        self.assertListEqual(list(np.array(struct_feat_2s).shape), [2, 128])
 
 
 if __name__ == "__main__":