TST: Refactor test_handle_adjustment.
TST: Refactor test_handle_adjustment.

Pull all the expected_result calculations into a helper.

dmitriz/zipline,magne-max/zipline-ja,florentchandelier/zipline,humdings/zipline,nborggren/zipline,jimgoo/zipline-fork,humdings/zipline,umuzungu/zipline,quantopian/zipline,nborggren/zipline,florentchandelier/zipline,wilsonkichoi/zipline,alphaBenj/zipline,umuzungu/zipline,otmaneJai/Zipline,bartosh/zipline,jimgoo/zipline-fork,otmaneJai/Zipline,wilsonkichoi/zipline,ChinaQuants/zipline,Scapogo/zipline,bartosh/zipline,grundgruen/zipline,dmitriz/zipline,grundgruen/zipline,Scapogo/zipline,magne-max/zipline-ja,enigmampc/catalyst,ChinaQuants/zipline,enigmampc/catalyst,quantopian/zipline,alphaBenj/zipline