--- a/tests/test-parents
+++ b/tests/test-parents
@@ -13,6 +13,12 @@ echo a >> a
 hg ci -Ama -d '1 0'
 echo b >> b
 hg ci -Amb -d '2 0'
+echo c > c
+hg ci -Amc -d '3 0'
+hg up -C 1
+echo d > c
+hg ci -Amc2 -d '4 0'
+hg up -C 3
 
 echo % hg parents
 hg parents
@@ -20,6 +26,12 @@ hg parents
 echo % hg parents a
 hg parents a
 
+echo % hg parents c, single revision
+hg parents c
+
+echo % hg parents -r 3 c
+hg parents -r 3 c
+
 echo % hg parents -r 2
 hg parents -r 2
 
@@ -41,4 +53,15 @@ echo '% hg parents -r 2 glob:a'
 cd ..
 hg parents -r 2 glob:a
 
+echo % merge working dir with 2 parents, hg parents c
+HGMERGE=true hg merge
+hg parents c
+
+echo % merge working dir with 1 parent, hg parents
+hg up -C 2
+HGMERGE=true hg merge -r 4
+hg parents
+echo % merge working dir with 1 parent, hg parents c
+hg parents c
+
 true