diff --git a/tests/conftest.py b/tests/conftest.py
index d5406bc..ceba3cd 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -6,12 +6,15 @@ import shutil
 import torch
 
 import pytest
+import matplotlib
 from torch.utils.data import Dataset
 
 from khaosz.core import *
 from khaosz.trainer import *
 from khaosz.trainer.data_util import *
 
+matplotlib.use("Agg")
+
 @pytest.fixture
 def base_test_env():
     test_dir = tempfile.mkdtemp()