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_prompt_buffer.vim b/src/testdir/test_prompt_buffer.vim
index e13f9a6..fb5d134 100644
--- a/src/testdir/test_prompt_buffer.vim
+++ b/src/testdir/test_prompt_buffer.vim
@@ -132,6 +132,16 @@
   normal! i
   call assert_beeps('normal! dd')
   call assert_beeps('normal! ~')
+  call assert_beeps('normal! o')
+  call assert_beeps('normal! O')
+  call assert_beeps('normal! p')
+  call assert_beeps('normal! P')
+  call assert_beeps('normal! u')
+  call assert_beeps('normal! ra')
+  call assert_beeps('normal! s')
+  call assert_beeps('normal! S')
+  call assert_beeps("normal! \<C-A>")
+  call assert_beeps("normal! \<C-X>")
   close!
 endfunc