diff --git a/tools/test.py b/tools/test.py
index e33a0c4315d86e04cfcaa07ef1d7a7b3b57249ce..0078db5a197131bc76392eb515b74a1fc4a065aa 100644
--- a/tools/test.py
+++ b/tools/test.py
@@ -128,6 +128,10 @@ def parse_args():
 def main():
     args = parse_args()
 
+    assert args.out or args.show, \
+        ('Please specify at least one operation (save or show the results) '
+         'with the argument "--out" or "--show"')
+
     if args.out is not None and not args.out.endswith(('.pkl', '.pickle')):
         raise ValueError('The output file must be a pkl file.')