patch 8.2.0275: some Ex code not covered by tests

Problem:    Some Ex code not covered by tests.
Solution:   Add test cases. (Yegappan Lakshmanan, closes #5659)
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 3b07104..a16329b 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -2358,4 +2358,28 @@
   setglobal spellfile=
 endfunc
 
+" Test closing a window or editing another buffer from a FileChangedRO handler
+" in a readonly buffer
+func Test_FileChangedRO_winclose()
+  augroup FileChangedROTest
+    au!
+    autocmd FileChangedRO * quit
+  augroup END
+  new
+  set readonly
+  call assert_fails('normal i', 'E788:')
+  close
+  augroup! FileChangedROTest
+
+  augroup FileChangedROTest
+    au!
+    autocmd FileChangedRO * edit Xfile
+  augroup END
+  new
+  set readonly
+  call assert_fails('normal i', 'E788:')
+  close
+  augroup! FileChangedROTest
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab