patch 8.0.0861: still many old style tests

Problem:    Still many old style tests.
Solution:   Convert several tests to new style. (Yegappan Lakshmanan)
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 95b4cb9..dede9fa 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -613,3 +613,22 @@
   call test_override('starting', 0)
   "delfunc! AutoCommandOptionSet
 endfunc
+
+" Test for Bufleave autocommand that deletes the buffer we are about to edit.
+func Test_BufleaveWithDelete()
+  new | edit Xfile1
+
+  augroup test_bufleavewithdelete
+      autocmd!
+      autocmd BufLeave Xfile1 bwipe Xfile2
+  augroup END
+
+  call assert_fails('edit Xfile2', 'E143:')
+  call assert_equal('Xfile1', bufname('%'))
+
+  autocmd! test_bufleavewithdelete BufLeave Xfile1
+  augroup! test_bufleavewithdelete
+
+  new
+  bwipe! Xfile1
+endfunc