I already use this crate, look who is author of question that you linked.
The problem in automatization,
yes I can write, and at now I actually do it:
#[cfg(test)]
impl PartialEq for Foo {
}
but several time I added new data field to struct Foo, and
forget update imp PartialEq, so at now I am looking for derive/proc_macro that automate things for me.