Macro skip_if_missing 

macro_rules! skip_if_missing {
    ($source:expr, $name:expr) => { ... };
}

Early-return a test when a pro .pedal file is absent.

let source = skip_if_missing!(
    load_pro_pedal_sub("pedals/legends/screamer.pedal"),
    "pedals/legends/screamer.pedal"
);

Expands to match $source { Some(s) => s, None => { eprintln!(…); return; } }. The enclosing #[test] function returns (), so the harness records a pass.