Avoid writing files in running tests

test/file_IO/test_file_IO.py

@@ -1,6 +1,8 @@
 """Tests of Phono3py API."""
 
+import os
 import pathlib
+import tempfile
 from collections.abc import Sequence
 from typing import Optional
 
@@ -11,7 +13,6 @@ from phono3py import Phono3py
 from phono3py.file_IO import _get_filename_suffix
 
 cwd = pathlib.Path(__file__).parent
-cwd_called = pathlib.Path.cwd()
 
 
 def test_kappa_filename():
@@ -60,10 +61,16 @@ def test_kappa_hdf5_with_boundary_mpf(si_pbesol: Phono3py):
     ]
 
     boundary_mfp = 10000.0
+
+    with tempfile.TemporaryDirectory() as temp_dir:
+        original_cwd = pathlib.Path.cwd()
+        os.chdir(temp_dir)
+
+        try:
             kappa_filename = _set_kappa(
                 si_pbesol, [4, 4, 4], write_kappa=True, boundary_mfp=boundary_mfp
             )
-    file_path = pathlib.Path(cwd_called / kappa_filename)
+            file_path = pathlib.Path(kappa_filename)
             with h5py.File(file_path, "r") as f:
                 np.testing.assert_almost_equal(f["boundary_mfp"][()], boundary_mfp)
                 assert set(list(f)) == set(key_ref)
@@ -71,6 +78,9 @@ def test_kappa_hdf5_with_boundary_mpf(si_pbesol: Phono3py):
             if file_path.exists():
                 file_path.unlink()
 
+        finally:
+            os.chdir(original_cwd)
+
 
 def _set_kappa(
     ph3: Phono3py,