--- a/tests/test-topic.t	Wed Jun 10 15:26:50 2015 -0400
+++ b/tests/test-topic.t	Wed Jun 10 15:03:39 2015 -0400
@@ -14,7 +14,8 @@
   
   options:
   
-    --clear clear active topic if any
+    --clear        clear active topic if any
+    --change VALUE revset of existing revisions to change topic
   
   (some details hidden, use --verbose to show complete help)
   $ hg topics
@@ -438,3 +439,77 @@
   |
   $ hg topics
      fran
+Changing topic fails if we don't give a topic
+  $ hg topic --change 9
+  abort: changing topic requires a topic name or --clear
+  [255]
+
+Can't change topic of a public change
+  $ hg topic --change 1:: --clear
+  abort: can't change topic of a public change
+  [255]
+
+Can clear topics
+  $ hg topic --change 9 --clear
+  changed topic on 1 changes
+  please run hg evolve --rev "not topic()" now
+  $ hg log -Gr 'draft() and not obsolete()'
+  o  changeset:   11:783930e1d79e
+  |  tag:         tip
+  |  parent:      3:a53952faf762
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     start on fran
+  |
+  | @  changeset:   10:4073470c35e1
+  | |  user:        test
+  | |  date:        Thu Jan 01 00:00:00 1970 +0000
+  | |  summary:     fran?
+  | |
+
+Normally you'd do this with evolve, but we'll use rebase to avoid
+bonus deps in the testsuite.
+
+  $ hg rebase -d tip -s .
+  rebasing 10:4073470c35e1 "fran?"
+
+Can add a topic to an existing change
+  $ hg topic --change 11 wat
+  changed topic on 1 changes
+  please run hg evolve --rev "topic(wat)" now
+  $ hg log -Gr 'draft() and not obsolete()'
+  o  changeset:   13:d91cd8fd490e
+  |  tag:         tip
+  |  topic:       wat
+  |  parent:      3:a53952faf762
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     start on fran
+  |
+  | @  changeset:   12:d9e32f4c4806
+  | |  user:        test
+  | |  date:        Thu Jan 01 00:00:00 1970 +0000
+  | |  summary:     fran?
+  | |
+
+Normally you'd do this with evolve, but we'll use rebase to avoid
+bonus deps in the testsuite.
+
+  $ hg rebase -d tip -s .
+  rebasing 12:d9e32f4c4806 "fran?"
+
+  $ hg log -Gr 'draft()'
+  @  changeset:   14:cf24ad8bbef5
+  |  tag:         tip
+  |  topic:       wat
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     fran?
+  |
+  o  changeset:   13:d91cd8fd490e
+  |  topic:       wat
+  |  parent:      3:a53952faf762
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     start on fran
+  |