Add unittest of AxisConcatenator.__len__
Add unittest of AxisConcatenator.__len__

wkentaro/chainer,niboshi/chainer,hvy/chainer,aonotas/chainer,kiyukuta/chainer,okuta/chainer,cupy/cupy,jnishi/chainer,ronekko/chainer,niboshi/chainer,chainer/chainer,ktnyt/chainer,tkerola/chainer,hvy/chainer,rezoo/chainer,ktnyt/chainer,okuta/chainer,chainer/chainer,chainer/chainer,keisuke-umezawa/chainer,niboshi/chainer,keisuke-umezawa/chainer,jnishi/chainer,wkentaro/chainer,hvy/chainer,delta2323/chainer,kashif/chainer,pfnet/chainer,cupy/cupy,anaruse/chainer,keisuke-umezawa/chainer,niboshi/chainer,cupy/cupy,jnishi/chainer,ktnyt/chainer,hvy/chainer,okuta/chainer,keisuke-umezawa/chainer,okuta/chainer,wkentaro/chainer,ktnyt/chainer,ysekky/chainer,wkentaro/chainer,chainer/chainer,cupy/cupy,jnishi/chainer