--- a/tests/test-template-functions.t	Mon Mar 23 15:14:42 2020 -0700
+++ b/tests/test-template-functions.t	Thu Mar 26 00:07:12 2020 +0900
@@ -1616,6 +1616,15 @@
    ]
   ]
 
+  $ hg log -T "{dict(foo=revset('.'))|cbor}" -R a -l1 | "$PYTHON" "$TESTTMP/decodecbor.py"
+  [
+   {
+    'foo': [
+     10
+    ]
+   }
+  ]
+
 json filter should escape HTML tags so that the output can be embedded in hgweb:
 
   $ hg log -T "{'<foo@example.org>'|json}\n" -R a -l1