Hipache is built on top of node-http-proxy [1], a nodejs library which implements a lot of the actual websocket logic. Most of the tests you have in mind are in that library. Hipache implements a management and automation layer on top of it, and although more tests are always good, in my experience full-stack integration tests are more important in that context. I am not the author, but I work at dotCloud and can tell you that Hipache was submitted to
massive amounts of integration testing and load testing before even touching its first production deployment. Obviously there's a long way to go before being as battle-tested as squid or nginx, but we're not talking about a week-end hack project either.
[1] http://github.com/nodejitsu/node-http-proxy