diff --git a/tests/test_minimal.py b/tests/test_minimal.py
index f64d92f..ff3d738 100644
--- a/tests/test_minimal.py
+++ b/tests/test_minimal.py
@@ -17,4 +17,4 @@ def test_survey():
         ),
         step=30.
     )
-    return survey
+    assert isinstance(survey, we.survey.Survey)