context 'when current user is a TA but NOT the TA of course which current assignment belongs to' do
      it 'refuses certain action' do
        stub_current_user(ta, ta.role.name, ta.role)
        allow(TaMapping).to receive(:exists?).with(ta_id: 8, course_id: 1).and_return(false )
        expect(controller.send(:action_allowed?)).to be false