It looks like you need to use conditional compilation to use Loom, which probably works okay for testing one library, but is pretty intrusive: #[cfg(loom)]

It looks like you need to use conditional compilation to use Loom, which probably works okay for testing one library, but is pretty intrusive: #[cfg(loom)] pub(crate) use loom::sync::atomic::AtomicUsize; #[cfg(not(loom))] pub(crate) use std::sync::atomic::AtomicUsize; I wonder if there are any languages that do a better job of letting you use your own scheduler?