vim-patch:8.2.5109: mode not updated after CTRL-O CTRL-C in Insert mode

Problem:    Mode not updated after CTRL-O CTRL-C in Insert mode.
Solution:   Set redraw_mode and use it. (closes vim/vim#10581)
7a1d32809b

src/nvim/testdir/test_normal.vim

@@ -3,6 +3,7 @@
 source shared.vim
 source check.vim
 source view_util.vim
+source screendump.vim
 
 func Setup_NewWindow()
   10new
@@ -2038,9 +2039,9 @@ func Test_normal33_g_cmd2()
   call assert_equal(2, line('.'))
   call assert_fails(':norm! g;', 'E662')
   call assert_fails(':norm! g,', 'E663')
-  let &ul=&ul
+  let &ul = &ul
   call append('$', ['a', 'b', 'c', 'd'])
-  let &ul=&ul
+  let &ul = &ul
   call append('$', ['Z', 'Y', 'X', 'W'])
   let a = execute(':changes')
   call assert_match('2\s\+0\s\+2', a)
@@ -2889,6 +2890,20 @@ func Test_message_when_using_ctrl_c()
   bwipe!
 endfunc
 
+func Test_mode_updated_after_ctrl_c()
+  CheckScreendump
+
+  let buf = RunVimInTerminal('', {'rows': 5})
+  call term_sendkeys(buf, "i")
+  call term_sendkeys(buf, "\<C-O>")
+  " wait a moment so that the "-- (insert) --" message is displayed
+  call TermWait(buf, 50)
+  call term_sendkeys(buf, "\<C-C>")
+  call VerifyScreenDump(buf, 'Test_mode_updated_1', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 " Test for '[m', ']m', '[M' and ']M'
 " Jumping to beginning and end of methods in Java-like languages
 func Test_java_motion()