trait SomeTrait {
    fn def(&self) -> bool {
        false
    }
}

struct SomeStruct;

#[cfg(not(test))]
impl SomeTrait for SomeStruct {}

#[cfg(test)]
mod tests {
    use super::*;

    impl SomeTrait for SomeStruct {
        fn def(&self) -> bool{
           true
        }
    }

    #[test]
    fn it_works() {
        let s = SomeStruct {};

        assert!(s.def());
    }

}


fn main(){
     let s = SomeStruct {};

     assert!(s.def());
}