I agree it's a little bit dirty here..
Do you mean just do `assert` directly? I think the subject.photo is set during initializing when looking contacts:
https://github.com/mozilla-b2g/gaia/blob/master/apps/communications/dialer/js/handled_call.js#L171
where `mock_contacts.js` always returns `contact.photo = ' test' `.
So I think without creating second call we may need to do something on mock..
(something like having a specific number without photo?)