diff --git a/tests/test_phonon.py b/tests/test_phonon.py
index ebb24b4..1e88207 100644
--- a/tests/test_phonon.py
+++ b/tests/test_phonon.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import inspect
 import os
 from typing import TYPE_CHECKING
 
@@ -16,38 +17,60 @@
     from pymatgen.core import Structure
 
 
-def test_phonon_calc(Li2O: Structure, M3GNetCalc: M3GNetCalculator, tmp_path: Path) -> None:
+@pytest.mark.parametrize(
+    ("force_const_file", "band_struct_file", "dos_file", "phonon_file"),
+    [("", "", "", ""), ("fc", "bs.yaml", "dos.dat", "ph.yaml")],
+)
+def test_phonon_calc(
+    Li2O: Structure,
+    M3GNetCalc: M3GNetCalculator,
+    tmp_path: Path,
+    force_const_file: str,
+    band_struct_file: str,
+    dos_file: str,
+    phonon_file: str,
+) -> None:
     """Tests for PhononCalc class"""
     # Note that the fmax is probably too high. This is for testing purposes only.
 
     # change dir to tmp_path
-    force_constants = tmp_path / "force_constants"
-    band_structure_yaml = tmp_path / "band_structure.yaml"
-    total_dos_dat = tmp_path / "total_dos.dat"
-    phonon_yaml = tmp_path / "phonon.yaml"
+    force_constants = tmp_path / force_const_file if force_const_file else False
+    band_structure_yaml = tmp_path / band_struct_file if band_struct_file else False
+    total_dos_dat = tmp_path / dos_file if dos_file else False
+    phonon_yaml = tmp_path / phonon_file if phonon_file else False
+    write_kwargs = {
+        "write_force_constants": force_constants,
+        "write_band_structure": band_structure_yaml,
+        "write_total_dos": total_dos_dat,
+        "write_phonon": phonon_yaml,
+    }
     phonon_calc = PhononCalc(
-        M3GNetCalc,
+        calculator=M3GNetCalc,
         supercell_matrix=((2, 0, 0), (0, 2, 0), (0, 0, 2)),
         fmax=0.1,
         t_step=50,
         t_max=1000,
-        write_force_constants=force_constants,
-        write_band_structure=band_structure_yaml,
-        write_total_dos=total_dos_dat,
-        write_phonon=phonon_yaml,
+        **write_kwargs,  # type: ignore[arg-type]
     )
     result = phonon_calc.calc(Li2O)
 
     # Test values at 100 K
-    ind = result["thermal_properties"]["temperatures"].tolist().index(300)
-    assert result["thermal_properties"]["heat_capacity"][ind] == pytest.approx(58.42898370395005, rel=1e-2)
-    assert result["thermal_properties"]["entropy"][ind] == pytest.approx(49.3774618162247, rel=1e-2)
-    assert result["thermal_properties"]["free_energy"][ind] == pytest.approx(13.245478097108784, rel=1e-2)
+    thermal_props = result["thermal_properties"]
+    ind = thermal_props["temperatures"].tolist().index(300)
+    assert thermal_props["heat_capacity"][ind] == pytest.approx(58.42898, rel=1e-2)
+    assert thermal_props["entropy"][ind] == pytest.approx(49.37746, rel=1e-2)
+    assert thermal_props["free_energy"][ind] == pytest.approx(13.24547, rel=1e-2)
 
     results = list(phonon_calc.calc_many([Li2O, Li2O]))
     assert len(results) == 2
 
-    assert os.path.isfile(force_constants)
-    assert os.path.isfile(band_structure_yaml)
-    assert os.path.isfile(total_dos_dat)
-    assert os.path.isfile(phonon_yaml)
+    ph_calc_params = inspect.signature(PhononCalc).parameters
+    # get all keywords starting with write_ and their default values
+    file_write_defaults = {key: val.default for key, val in ph_calc_params.items() if key.startswith("write_")}
+    assert len(file_write_defaults) == 4
+
+    for keyword, default_path in file_write_defaults.items():
+        if instance_val := write_kwargs[keyword]:
+            assert os.path.isfile(str(instance_val))
+        elif not default_path and not instance_val:
+            assert not os.path.isfile(default_path)