diff --git a/pymatgen/analysis/defects/supercells.py b/pymatgen/analysis/defects/supercells.py
index 89a72168..aaa84203 100644
--- a/pymatgen/analysis/defects/supercells.py
+++ b/pymatgen/analysis/defects/supercells.py
@@ -65,7 +65,7 @@ def get_matched_structure_mapping_old(
     uc_struct: Structure,
     sc_struct: Structure,
     sm: StructureMatcher | None = None,
-) -> tuple[NDArray, ArrayLike] | None:
+) -> tuple[NDArray, ArrayLike] | None:  # pragma: no cover
     """Get the mapping of the supercell to the unit cell.
 
     Get the mapping from the supercell structure onto the base structure,
diff --git a/tests/test_supercells.py b/tests/test_supercells.py
index bd12a4ca..1ef169a7 100644
--- a/tests/test_supercells.py
+++ b/tests/test_supercells.py
@@ -7,6 +7,7 @@
     get_sc_fromstruct,
     get_closest_sc_mat
 )
+import pytest
 
 
 def test_supercells(gan_struct):
@@ -28,6 +29,9 @@ def test_ase_supercells(gan_struct):
     sc = gan_struct * sc_mat
     assert 4 <= sc.num_sites <= 8
 
+    # check raise
+    with pytest.raises(RuntimeError):
+        _ase_cubic(gan_struct, min_atoms=4, max_atoms=8, min_length=10)
 
 
 def test_closest_sc_mat(test_dir):