diff --git a/src/testdir/test_gui.vim b/src/testdir/test_gui.vim
index 3472012..e935e5f 100644
--- a/src/testdir/test_gui.vim
+++ b/src/testdir/test_gui.vim
@@ -882,7 +882,7 @@
   new
   call setline(1, ['one two three', 'four five six'])
 
-  " place the cursor using left click
+  " place the cursor using left click in normal mode
   call cursor(1, 1)
   call test_gui_mouse_event(0, 2, 4, 0, 0)
   call test_gui_mouse_event(3, 2, 4, 0, 0)
@@ -1092,9 +1092,70 @@
   set mouse&
   let &guioptions = save_guioptions
 
+  " Test invalid parameters for test_gui_mouse_event()
+  call assert_fails('call test_gui_mouse_event("", 1, 2, 3, 4)', 'E474:')
+  call assert_fails('call test_gui_mouse_event(0, "", 2, 3, 4)', 'E474:')
+  call assert_fails('call test_gui_mouse_event(0, 1, "", 3, 4)', 'E474:')
+  call assert_fails('call test_gui_mouse_event(0, 1, 2, "", 4)', 'E474:')
+  call assert_fails('call test_gui_mouse_event(0, 1, 2, 3, "")', 'E474:')
+
   bw!
   call test_override('no_query_mouse', 0)
   set mousemodel&
 endfunc
 
+" Test for 'guitablabel' and 'guitabtooltip' options
+func TestGuiTabLabel()
+  call add(g:TabLabels, v:lnum + 100)
+  let bufnrlist = tabpagebuflist(v:lnum)
+  return bufname(bufnrlist[tabpagewinnr(v:lnum) - 1])
+endfunc
+
+func TestGuiTabToolTip()
+  call add(g:TabToolTips, v:lnum + 200)
+  let bufnrlist = tabpagebuflist(v:lnum)
+  return bufname(bufnrlist[tabpagewinnr(v:lnum) - 1])
+endfunc
+
+func Test_gui_tablabel_tooltip()
+  %bw!
+  " Removing the tabline at the end of this test, reduces the window height by
+  " one. Save and restore it after the test.
+  let save_lines = &lines
+  edit one
+  set modified
+  tabnew two
+  set modified
+  tabnew three
+  set modified
+  let g:TabLabels = []
+  set guitablabel=%{TestGuiTabLabel()}
+  call test_override('starting', 1)
+  redrawtabline
+  call test_override('starting', 0)
+  call assert_true(index(g:TabLabels, 101) != -1)
+  call assert_true(index(g:TabLabels, 102) != -1)
+  call assert_true(index(g:TabLabels, 103) != -1)
+  set guitablabel&
+  unlet g:TabLabels
+
+  if has('gui_gtk')
+    " Only on GTK+, the tooltip function is called even if the mouse is not
+    " on the tabline. on Win32 and Motif, the tooltip function is called only
+    " when the mouse pointer is over the tabline.
+    let g:TabToolTips = []
+    set guitabtooltip=%{TestGuiTabToolTip()}
+    call test_override('starting', 1)
+    redrawtabline
+    call test_override('starting', 0)
+    call assert_true(index(g:TabToolTips, 201) != -1)
+    call assert_true(index(g:TabToolTips, 202) != -1)
+    call assert_true(index(g:TabToolTips, 203) != -1)
+    set guitabtooltip&
+    unlet g:TabToolTips
+  endif
+  %bw!
+  let &lines = save_lines
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab