Shared via Rust Playground

playground.rs

use std::path::Path;

#[cfg(test)]
thread_local! (pub static FAIL: AtomicBool = AtomicBool::new (false));

#[cfg(not(test))]
#[inline]
fn testable_rename<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> std::io::Result<()> {
    std::fs::rename(from, to)
}

#[cfg(test)]
fn testable_rename<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> std::io::Result<()> {
    let fail = FAIL.with(|f| f.load(Ordering::Relaxed));
    if fail {
        return Err(std::io::Error::new(ErrorKind::NotFound, "ups"));
    }
    std::fs::rename(from, to)
}

#[test]
fn test_something_that_uses_rename() {
    FAIL.with(|f| f.store(true, Ordering::Relaxed));
    // ...
}

fn main() {}