[mercari Summer Internship 2017 Qualification] improve tests
[mercari Summer Internship 2017 Qualification] improve tests

mikoim/funstuff,mikoim/funstuff,mikoim/funstuff,mikoim/funstuff,mikoim/funstuff,mikoim/funstuff,mikoim/funstuff,mikoim/funstuff,mikoim/funstuff