diff --git a/test/util.py b/test/util.py
index b1f2cac..23a78b9 100644
--- a/test/util.py
+++ b/test/util.py
@@ -1,3 +1,4 @@
+import base64
 import mapsy
 from contextlib import contextmanager
 from os import path
@@ -29,4 +30,8 @@ def assert_render_equality(
     assert path.exists(output_path)
     with open(output_path, "rb") as f:
         with open(input_path, "rb") as f_ref:
-            assert f.read() == f_ref.read()
+            f_data = f.read()
+            f_ref_data = f_ref.read()
+            if f_data != f_ref_data:
+                print(f"image with issue: {base64.b64encode(f_ref_data)}")
+            assert f_data == f_ref_data