patch 8.0.0485: not all windows commands are tested

Problem:    Not all windows commands are tested.
Solution:   Add more tests for windows commands. (Dominique Pelle,
            closes #1575) Run test_autocmd separately, it interferes with
            other tests.  Fix tests that depended on side effects.
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 228e7ab..2a0c1cf 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -460,8 +460,8 @@
   let bd = getbufvar(bnr, '',def_num)
   call assert_equal(1, len(bd))
 
-  call assert_equal('', getbufvar(9, ''))
-  call assert_equal(def_num, getbufvar(9, '', def_num))
+  call assert_equal('', getbufvar(9999, ''))
+  call assert_equal(def_num, getbufvar(9999, '', def_num))
   unlet def_num
 
   call assert_equal(0, getbufvar(bnr, '&autoindent'))