diff --git a/tests/files/performance/import_time_linux.json b/tests/files/performance/import_time_linux.json
new file mode 100644
index 00000000000..3492c93a840
--- /dev/null
+++ b/tests/files/performance/import_time_linux.json
@@ -0,0 +1,19 @@
+{
+    "from pymatgen.core.bonds import CovalentBond": 289.5851116666108,
+    "from pymatgen.core.composition import Composition": 292.8479909999548,
+    "from pymatgen.core.interface import Interface": 969.5693099999593,
+    "from pymatgen.core.ion import Ion": 291.07530133334575,
+    "from pymatgen.core.lattice import Lattice": 288.8340153333881,
+    "from pymatgen.core.libxcfunc import LibxcFunc": 293.4184753333587,
+    "from pymatgen.core.molecular_orbitals import MolecularOrbitals": 294.19796566658835,
+    "from pymatgen.core.operations import SymmOp": 296.4627546666634,
+    "from pymatgen.core.periodic_table import Element": 295.95872066662804,
+    "from pymatgen.core.sites import Site": 292.66485499999817,
+    "from pymatgen.core.spectrum import Spectrum": 486.72776566669046,
+    "from pymatgen.core.structure import Structure": 291.01618733333606,
+    "from pymatgen.core.surface import Slab": 301.90875833329756,
+    "from pymatgen.core.tensors import Tensor": 304.27744800003137,
+    "from pymatgen.core.trajectory import Trajectory": 300.45536066666045,
+    "from pymatgen.core.units import Unit": 305.4779056666348,
+    "from pymatgen.core.xcfunc import XcFunc": 309.1085626666275
+}
\ No newline at end of file
diff --git a/tests/files/performance/import_time_macos.json b/tests/files/performance/import_time_macos.json
new file mode 100644
index 00000000000..9ac1e63fc9d
--- /dev/null
+++ b/tests/files/performance/import_time_macos.json
@@ -0,0 +1,19 @@
+{
+    "from pymatgen.core.bonds import CovalentBond": 321.8502360000457,
+    "from pymatgen.core.composition import Composition": 292.35445800009074,
+    "from pymatgen.core.interface import Interface": 855.005861000033,
+    "from pymatgen.core.ion import Ion": 240.8930970000256,
+    "from pymatgen.core.lattice import Lattice": 329.09868066659936,
+    "from pymatgen.core.libxcfunc import LibxcFunc": 306.6966386666839,
+    "from pymatgen.core.molecular_orbitals import MolecularOrbitals": 281.78087466661356,
+    "from pymatgen.core.operations import SymmOp": 299.9741943333447,
+    "from pymatgen.core.periodic_table import Element": 293.6565829999533,
+    "from pymatgen.core.sites import Site": 280.3443330000543,
+    "from pymatgen.core.spectrum import Spectrum": 459.20266666666976,
+    "from pymatgen.core.structure import Structure": 265.4675833332476,
+    "from pymatgen.core.surface import Slab": 306.0919996667053,
+    "from pymatgen.core.tensors import Tensor": 310.54281933325,
+    "from pymatgen.core.trajectory import Trajectory": 335.25658333329983,
+    "from pymatgen.core.units import Unit": 294.03472200003006,
+    "from pymatgen.core.xcfunc import XcFunc": 309.3993196666058
+}
\ No newline at end of file
diff --git a/tests/files/performance/import_time_windows.json b/tests/files/performance/import_time_windows.json
new file mode 100644
index 00000000000..270b73a9d65
--- /dev/null
+++ b/tests/files/performance/import_time_windows.json
@@ -0,0 +1,19 @@
+{
+    "from pymatgen.core.bonds import CovalentBond": 443.7560000000455,
+    "from pymatgen.core.composition import Composition": 441.06553333335796,
+    "from pymatgen.core.interface import Interface": 1828.751033333295,
+    "from pymatgen.core.ion import Ion": 443.58053333333675,
+    "from pymatgen.core.lattice import Lattice": 445.729999999988,
+    "from pymatgen.core.libxcfunc import LibxcFunc": 459.24773333338936,
+    "from pymatgen.core.molecular_orbitals import MolecularOrbitals": 440.4825999999957,
+    "from pymatgen.core.operations import SymmOp": 440.62226666665083,
+    "from pymatgen.core.periodic_table import Element": 441.64050000002436,
+    "from pymatgen.core.sites import Site": 442.1802333333744,
+    "from pymatgen.core.spectrum import Spectrum": 737.3025000000174,
+    "from pymatgen.core.structure import Structure": 445.0546333332568,
+    "from pymatgen.core.surface import Slab": 463.0683333333157,
+    "from pymatgen.core.tensors import Tensor": 463.5761666666743,
+    "from pymatgen.core.trajectory import Trajectory": 443.9995333333779,
+    "from pymatgen.core.units import Unit": 446.352766666602,
+    "from pymatgen.core.xcfunc import XcFunc": 469.42599999996065
+}
\ No newline at end of file
diff --git a/tests/performance/test_import_time.py b/tests/performance/test_import_time.py
index 49adb49cddd..9b52ee51c34 100644
--- a/tests/performance/test_import_time.py
+++ b/tests/performance/test_import_time.py
@@ -1,7 +1,9 @@
 """
 Test the import time of several important modules.
+
+NOTE:
+    - Toggle the "GEN_REF_TIME" to generate reference import time.
 """
-# ruff: noqa: T201 (check for print statement)
 
 from __future__ import annotations
 
@@ -9,17 +11,20 @@
 import os
 import subprocess
 import time
+import warnings
 from typing import TYPE_CHECKING
 
 import pytest
 
+from pymatgen.util.testing import TEST_FILES_DIR
+
 if TYPE_CHECKING:
     from typing import Literal
 
-# Toggle this to generate reference import times
-GEN_REF_TIME = True
+# NOTE: Toggle this to generate reference import time
+GEN_REF_TIME: bool = False
 
-MODULES_TO_TEST = (
+MODULES_TO_TEST: tuple[str, ...] = (
     "from pymatgen.core.bonds import CovalentBond",
     "from pymatgen.core.composition import Composition",
     "from pymatgen.core.interface import Interface",
@@ -40,9 +45,10 @@
 )
 
 # Get runner OS and reference file
-RUNNER_OS: Literal["linux", "windows", "macos"] = os.getenv("RUNNER_OS", "").lower()  # type: ignore[assignment]
+RUNNER_OS: Literal["linux", "windows", "macos"] = os.getenv("RUNNER_OS", "macos").lower()  # type: ignore[assignment]
 assert RUNNER_OS in {"linux", "windows", "macos"}
-REF_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), f"import_time_{RUNNER_OS}.json")
+
+REF_FILE: str = f"{TEST_FILES_DIR}/performance/import_time_{RUNNER_OS}.json"
 
 
 @pytest.mark.skipif(not GEN_REF_TIME, reason="Set GEN_REF_TIME to generate reference import time.")
@@ -69,11 +75,9 @@ def test_import_time(grace_percent: float = 0.20, hard_percent: float = 0.50) ->
         hard_percent (float): Maximum allowed percentage increase in import time
             before the test fails.
     """
-    try:
-        with open(REF_FILE, encoding="utf-8") as file:
-            ref_import_times = json.load(file)
-    except FileNotFoundError:
-        pytest.fail(f"Reference file {REF_FILE} not found. Please generate it.")
+
+    with open(REF_FILE, encoding="utf-8") as file:
+        ref_import_times = json.load(file)
 
     for module_import_cmd, ref_time in ref_import_times.items():
         current_time = _measure_import_time_in_ms(module_import_cmd)
@@ -86,9 +90,9 @@ def test_import_time(grace_percent: float = 0.20, hard_percent: float = 0.50) ->
             if current_time > hard_threshold:
                 pytest.fail(f"{module_import_cmd} import too slow! {hard_threshold=:.2f} ms")
             else:
-                pytest.warns(
-                    UserWarning,
+                warnings.warn(
                     f"{module_import_cmd} import slightly slower than reference: {grace_threshold=:.2f} ms",
+                    stacklevel=2,
                 )