Commented out, this test will never get run and so it's in very significant danger of breaking somewhere along the way. It's actually *not* hard to test, with deterministic destructor calling; given the condition is that you need each addition to match a deletion, I'd expect to use [task local storage](http://static.rust-lang.org/doc/master/std/local_data/index.html) for the test, maintaining therein a set of the numbers active (I think `extra::bitv` would do for this case and it should perform better than an unordered `Vec<int>`—you probably don't want to use `HashSet` in testing `HashMap`).