This will need to stay rather than being commented out. You can follow the same test strategy of crates like libcollections which have lots of #[cfg(test)] directives at the top.

Sure, there is one right down below, but it seems to make no effect whrn this one is on :(

Can you explain the errors that you're encountering?

The errors where simply that assert! (and friends) are not defined. Turns out that it's not enough to add #[cfg(test)] extern crate test;, which seemed like an obvious way of fixing this...

#[cfg(test)] #[phase(plugin, link)] extern crate std;

Following your advise I checked libcollections/lib.rs and adding the above for some reason fixes this. This still looks like a little issue in the compiler, don't you think?

Turns out that it's not enough to add #[cfg(test)] extern crate test;,

What is the error? (We'll be able to tell if it's a compiler issue if you tell us the error messages/problems. :) )

The error message without the extra attribute was this:

lib.rs:117:13: 117:22 error: macro undefined: 'assert_eq!'

I am now actually face with something more interesting:

error: type `&'static str` does not implement any method in scope named `len`

Ah, yes, if you're using macros from std (or core) you need to import them via a #[phase].

For len, it's a trait method so you need to have the traits in scope. (i.e. add a use std::collections::Collection in the module with the tests.)

This should be removed: #15815 (comment)

Why is there a new line?