new file mode 100644
--- /dev/null
+++ b/src/testdir/test_listener.vim
@@ -0,0 +1,77 @@
+" tests for listener_add() and listener_remove()
+
+func StoreList(l)
+  let g:list = a:l
+endfunc
+
+func AnotherStoreList(l)
+  let g:list2 = a:l
+endfunc
+
+func EvilStoreList(l)
+  let g:list3 = a:l
+  call assert_fails("call add(a:l, 'myitem')", "E742:")
+endfunc
+
+func Test_listening()
+  new
+  call setline(1, ['one', 'two'])
+  let id = listener_add({l -> StoreList(l)})
+  call setline(1, 'one one')
+  redraw
+  call assert_equal([{'lnum': 1, 'end': 2, 'col': 1, 'added': 0}], g:list)
+
+  " Two listeners, both get called.
+  let id2 = listener_add({l -> AnotherStoreList(l)})
+  let g:list = []
+  let g:list2 = []
+  exe "normal $asome\<Esc>"
+  redraw
+  call assert_equal([{'lnum': 1, 'end': 2, 'col': 8, 'added': 0}], g:list)
+  call assert_equal([{'lnum': 1, 'end': 2, 'col': 8, 'added': 0}], g:list2)
+
+  call listener_remove(id2)
+  let g:list = []
+  let g:list2 = []
+  call setline(3, 'three')
+  redraw
+  call assert_equal([{'lnum': 3, 'end': 3, 'col': 1, 'added': 1}], g:list)
+  call assert_equal([], g:list2)
+
+  " the "o" command first adds an empty line and then changes it
+  let g:list = []
+  exe "normal Gofour\<Esc>"
+  redraw
+  call assert_equal([{'lnum': 4, 'end': 4, 'col': 1, 'added': 1},
+	\ {'lnum': 4, 'end': 5, 'col': 1, 'added': 0}], g:list)
+
+  let g:list = []
+  call listener_remove(id)
+  call setline(1, 'asdfasdf')
+  redraw
+  call assert_equal([], g:list)
+
+  " Trying to change the list fails
+  let id = listener_add({l -> EvilStoreList(l)})
+  let g:list3 = []
+  call setline(1, 'asdfasdf')
+  redraw
+  call assert_equal([{'lnum': 1, 'end': 2, 'col': 1, 'added': 0}], g:list3)
+
+  bwipe!
+endfunc
+
+func Test_listening_other_buf()
+  new
+  call setline(1, ['one', 'two'])
+  let bufnr = bufnr('')
+  normal ww
+  let id = listener_add({l -> StoreList(l)}, bufnr)
+  let g:list = []
+  call setbufline(bufnr, 1, 'hello')
+  redraw
+  call assert_equal([{'lnum': 1, 'end': 2, 'col': 1, 'added': 0}], g:list)
+
+  exe "buf " .. bufnr
+  bwipe!
+endfunc