vim-patch:8.1.1193: typos and small problems in test files

Problem:    Typos and small problems in test files.
Solution:   Small improvements.
037c54f261

Include unmerged patch v8.0.1200 changes
because this patch depends on `set beloff=all` removed in 1 test.

src/nvim/testdir/test_gn.vim

@@ -1,9 +1,8 @@
 " Test for gn command
 
 func Test_gn_command()
-  set belloff=all
   noautocmd new
-  " replace a single char by itsself quoted:
+  " replace a single char by itself quoted:
   call setline('.', 'abc x def x ghi x jkl')
   let @/ = 'x'
   exe "norm! cgn'x'\<esc>.."
@@ -157,7 +156,6 @@ func Test_gn_command()
   sil! %d _
 
   set wrapscan&vim
-  set belloff&vim
 endfunc
 
 func Test_gN_repeat()

src/nvim/testdir/test_quotestar.vim

@@ -97,7 +97,7 @@ func Do_test_quotestar_for_x11()
   if has('unix') && has('gui') && !has('gui_running')
     let @* = ''
 
-    " Running in a terminal and the GUI is avaiable: Tell the server to open
+    " Running in a terminal and the GUI is available: Tell the server to open
     " the GUI and check that the remote command still works.
     " Need to wait for the GUI to start up, otherwise the send hangs in trying
     " to send to the terminal window.

src/nvim/testdir/test_registers.vim

@@ -109,6 +109,8 @@ func Test_recording_esc_sequence()
   bwipe!
   if exists('save_F2')
     let &t_F2 = save_F2
+  else
+    set t_F2=
   endif
 endfunc
 

src/nvim/testdir/test_tabpage.vim

@@ -142,9 +142,6 @@ endfunc
 
 " Test autocommands
 function Test_tabpage_with_autocmd()
-  if !has('autocmd')
-    return
-  endif
   command -nargs=1 -bar C :call add(s:li, '=== ' . <q-args> . ' ===')|<args>
   augroup TestTabpageGroup
     au!

src/nvim/testdir/test_vartabs.vim

@@ -5,6 +5,7 @@ if !has("vartabs")
 endif
 
 source view_util.vim
+
 func s:compare_lines(expect, actual)
   call assert_equal(join(a:expect, "\n"), join(a:actual, "\n"))
 endfunc
@@ -372,3 +373,9 @@ func Test_vartabs_failures()
   call assert_fails('set vts=,8')
   call assert_fails('set vsts=,8')
 endfunc
+
+func Test_vartabs_reset()
+  set vts=8
+  set all&
+  call assert_equal('', &vts)
+endfunc

src/nvim/testdir/test_visual.vim

@@ -255,7 +255,6 @@ func TriggerTheProblem()
 endfunc
 
 func Test_visual_mode_reset()
-  set belloff=all
   enew
   let g:msg = "Everything's fine."
   enew
@@ -268,7 +267,6 @@ func Test_visual_mode_reset()
   exe "normal! GV:call TriggerTheProblem()\<CR>"
   call assert_equal("Everything's fine.", g:msg)
 
-  set belloff&
 endfunc
 
 func Test_Visual_word_textobject()