Simplify code in testing.backend
Simplify code in testing.backend

chainer/chainer,okuta/chainer,hvy/chainer,hvy/chainer,wkentaro/chainer,wkentaro/chainer,keisuke-umezawa/chainer,niboshi/chainer,keisuke-umezawa/chainer,pfnet/chainer,chainer/chainer,niboshi/chainer,hvy/chainer,okuta/chainer,niboshi/chainer,wkentaro/chainer,okuta/chainer,niboshi/chainer,chainer/chainer,chainer/chainer,wkentaro/chainer,tkerola/chainer,hvy/chainer,keisuke-umezawa/chainer,okuta/chainer,keisuke-umezawa/chainer