patch 8.2.0369: various Normal mode commands not fully tested

Problem:    Various Normal mode commands not fully tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5751)
diff --git a/src/testdir/test_ex_mode.vim b/src/testdir/test_ex_mode.vim
index 95144dd..e50e6a5 100644
--- a/src/testdir/test_ex_mode.vim
+++ b/src/testdir/test_ex_mode.vim
@@ -158,4 +158,17 @@
         \ "E15: Invalid expression: \\\nm")
 endfunc
 
+func Test_ex_mode_errors()
+  " Not allowed to enter ex mode when text is locked
+  au InsertCharPre <buffer> normal! gQ<CR>
+  let caught_e523 = 0
+  try
+    call feedkeys("ix\<esc>", 'xt')
+  catch /^Vim\%((\a\+)\)\=:E523/ " catch E523
+    let caught_e523 = 1
+  endtry
+  call assert_equal(1, caught_e523)
+  au! InsertCharPre
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab