Test for autocommand that changes the buffer list, when doing ":ball".

STARTTEST
:au BufReadPost Xxx2 bdel
/start of
A1:.,/end of/w! Xxx1   " write test file Xxx1
$r2:.,/end of/w! Xxx2    " write test file Xxx2
$r3:.,/end of/w! Xxx3    " write test file Xxx3
$r4:ball                 " open window for all args, close Xxx2
:.,$w! test.out          " Write contents of this file
:w >>test.out        " Append contents of second window (Xxx1)
:/^start of/,$w >>test.out   " Append contents of last window (this file)
:!rm Xxx1 Xxx2 Xxx3
:qa!
ENDTEST

start of test file Xxx
	this is a test
	this is a test
end of test file Xxx