--- a/tests/test-topic-stack.t	Sun Dec 02 16:52:14 2018 +0100
+++ b/tests/test-topic-stack.t	Fri Sep 21 11:44:34 2018 -0400
@@ -229,8 +229,52 @@
   s1: c_c
   s0^ c_b (base)
 
+merge case (displaying info about external)
+-------------------------------------------
+
+  $ hg up default
+  0 files updated, 0 files merged, 4 files removed, 0 files unresolved
+  $ hg topics zzz
+  marked working directory as topic: zzz
+  $ echo zzz > zzz
+  $ hg add zzz
+  $ hg commit -m zzz_a
+  active topic 'zzz' grew its first changeset
+  (see 'hg help topics' for more information)
+  $ hg merge foo
+  4 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg commit -m "merged foo"
+
+stack -m display data about child
+
+  $ hg stack foo
+  ### topic: foo
+  ### target: default (branch)
+  s4: c_f
+  s3: c_e
+  s2: c_d
+  s1: c_c
+  s0^ c_b (base)
+
+  $ hg stack foo --children
+  ### topic: foo
+  ### target: default (branch)
+  s4: c_f (external-children)
+  s3: c_e
+  s2: c_d
+  s1: c_c
+  s0^ c_b (base)
+
 error case, nothing to list
 
+  $ hg strip --config extensions.strip= t1 --no-backup
+  0 files updated, 0 files merged, 5 files removed, 0 files unresolved
+
+  $ hg up foo
+  switching to topic foo
+  4 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
   $ hg topic --clear
   $ hg stack
   ### target: default (branch)