diff --git a/pkg/controller.v1beta1/experiment/manifest/generator_test.go b/pkg/controller.v1beta1/experiment/manifest/generator_test.go
index 9f89f5ac5f4..a2b9f295f0e 100644
--- a/pkg/controller.v1beta1/experiment/manifest/generator_test.go
+++ b/pkg/controller.v1beta1/experiment/manifest/generator_test.go
@@ -236,8 +236,8 @@ spec:
             - "--momentum=0.9"`
 
 	expectedRunSpec, err := util.ConvertStringToUnstructured(expectedStr)
-	if err != nil {
-		t.Errorf("%v: %v", errConvertStringToUnstructuredFailed, err)
+	if diff := cmp.Diff(nil, err, cmpopts.EquateErrors()); len(diff) != 0 {
+		t.Errorf("ConvertStringToUnstructured failed (-want,+got):\n%s", diff)
 	}
 
 	cases := map[string]struct {