diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..52ac544
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,8 @@
+"""conftest.py contains fixtures that are automatically imported by pytest."""
+import pytest
+import matplotlib
+
+
+@pytest.fixture(autouse=True, scope='session')
+def set_matplotlib_backend():
+    matplotlib.use('Agg')  # to avoid opening windows during testing