在Erlang的邮件列表中找到了解释：
We have seen the same issue with CouchDB. What we found out
is that in our case localhost was not only resolving to 127.0.0.1 (IPv4)
but also ::1 (IPv6) and that http:request() would try to connect to
::1 where no service was listening.

Erlang的http模块缺省是打开IPv6模式的，当测试程序通过http模块连接localhost时，连接的地址是IPv6的::1地址，但是mochi没有在此监听，所以连接出错 {error,econnrefused}

解决方法两种：
1. 将mochi-urls.txt中的地址都改成127.0.0.1
2. 在http:request(…)运行之前调用http:set_options([{ipv6,disabled}])，关闭测试程序的IPv6模式，使用IPv4模式

理论上还有一种方法：让mochi服务器开启IPv6模式监听，这个我不知道这么开，
参考
You should teach Yaws to listen also on IPv6 – “localhost” resolves not
only to IPv4 127.0.0.1, but also to IPv6 ::1.

有点跑题了，呵呵