diff --git a/tests/test-backout.out b/tests/test-backout.out
--- a/tests/test-backout.out
+++ b/tests/test-backout.out
@@ -1,3 +1,6 @@
+# should complain
+abort: please specify a revision to backout
+abort: please specify just one revision
 # basic operation
 adding a
 reverting a