new file mode 100644
--- /dev/null
+++ b/src/testdir/test_substitute.vim
@@ -0,0 +1,41 @@
+" Tests for multi-line regexps with ":s".
+
+function! Test_multiline_subst()
+  enew!
+  call append(0, ["1 aa",
+	      \ "bb",
+	      \ "cc",
+	      \ "2 dd",
+	      \ "ee",
+	      \ "3 ef",
+	      \ "gh",
+	      \ "4 ij",
+	      \ "5 a8",
+	      \ "8b c9",
+	      \ "9d",
+	      \ "6 e7",
+	      \ "77f",
+	      \ "xxxxx"])
+
+  1
+  " test if replacing a line break works with a back reference
+  /^1/,/^2/s/\n\(.\)/ \1/
+  " test if inserting a line break works with a back reference
+  /^3/,/^4/s/\(.\)$/\r\1/
+  " test if replacing a line break with another line break works
+  /^5/,/^6/s/\(\_d\{3}\)/x\1x/
+  call assert_equal('1 aa bb cc 2 dd ee', getline(1))
+  call assert_equal('3 e', getline(2))
+  call assert_equal('f', getline(3))
+  call assert_equal('g', getline(4))
+  call assert_equal('h', getline(5))
+  call assert_equal('4 i', getline(6))
+  call assert_equal('j', getline(7))
+  call assert_equal('5 ax8', getline(8))
+  call assert_equal('8xb cx9', getline(9))
+  call assert_equal('9xd', getline(10))
+  call assert_equal('6 ex7', getline(11))
+  call assert_equal('7x7f', getline(12))
+  call assert_equal('xxxxx', getline(13))
+  enew!
+endfunction