Add a regression test for #1459.
Merge branch 'pr-regression-1459' into iij
Merge branch 'iij' of github.com:iij/mruby into iij
Merge branch 'iij' of github.com:iij/mruby into iij
Merge branch 'iij' of github.com:iij/mruby into iij
Merge branch 'iij' of github.com:iij/mruby into iij
use assert_equal.