The mash directive is not necessarily really straight-forward in what it does, so writing a test for it would be nice. The general idea is:

Setup

use rpmfluff to create a directory containing fake rpm for i686 wine (taken randomly as an example of multilib package) and a i686 foobar rpm

Scenario 1

use the directive to run mash with arch set to i386

check that the directory still contains both rpms

Scenario 2

use the directive to run mash with arch set to x86_64

check that the directory contains just the i686 wine rpm