diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..245f763
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,4 @@
+import matplotlib
+
+# Force a non-GUI backend for all tests
+matplotlib.use("Agg", force=True)