--- a/tests/test-revset.t	Tue Jul 10 23:01:53 2018 +0900
+++ b/tests/test-revset.t	Thu Jul 12 23:07:29 2018 +0900
@@ -1063,6 +1063,12 @@
   8
   9
 
+test ancestor variants of empty revision
+
+  $ log 'ancestor(none())'
+  $ log 'ancestors(none())'
+  $ log 'commonancestors(none())'
+
 test ancestors with depth limit
 
  (depth=0 selects the node itself)