--- a/tests/test-template-functions.t	Sat Mar 21 13:27:47 2020 +0900
+++ b/tests/test-template-functions.t	Sat Mar 21 13:39:39 2020 +0900
@@ -1269,6 +1269,12 @@
   2147483647
   $ hg log -T '{revset("%d", rev)}\n' -r'null'
   -1
+  $ hg log -T '{revset("%d", rev + 1)}\n' -r'tip'
+  abort: unknown revision '3'!
+  [255]
+  $ hg log -T '{revset("%d", rev - 1)}\n' -r'null'
+  abort: unknown revision '-2'!
+  [255]
 
 Invalid arguments passed to revset()