#[cfg(test)] internal export hack

dep.rs

// HACK
#[cfg(test)]
pub use self::secret::internal;

mod secret {
    pub fn internal() -> bool {
        println!("you've broken my secret elbow!");
        true
    }
}

main.rs

mod dep;

#[cfg(not(test))]
fn main() {
    assert_eq!(dep::internal(), true);
}

#[cfg(test)]
#[test]
fn white_box() {
    assert_eq!(dep::internal(), true);
}

shell.output

$ rustc main.rs
main.rs:5:16: 5:29 error: unresolved name `dep::internal`.
main.rs:5     assert_eq!(dep::internal(), true);
                         ^~~~~~~~~~~~~
<std macros>:1:1: 14:2 note: in expansion of assert_eq!
main.rs:5:5: 5:39 note: expansion site
error: aborting due to previous error

$ rustc --test main.rs && ./main

running 1 test
test white_box ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured