--- a/tests/test-touch.t	Mon Mar 25 15:44:44 2019 -0700
+++ b/tests/test-touch.t	Mon Mar 25 15:45:11 2019 -0700
@@ -161,3 +161,12 @@
        rewritten(.*) as [0-9a-f]{12} using touch by test (.*) (re)
          note: testing with no successor
   
+
+Public phase
+
+  $ hg phase --public -r 2
+  $ hg touch 2
+  abort: cannot touch public changesets: * (glob)
+  (see 'hg help phases' for details)
+  [255]
+  $ hg touch --duplicate 2