Mocking long running trait

examples/long-running-trait/src/lib.rs

#![allow(dead_code)]


struct Rectangle {
    width: u64,
    length: u64,
}

pub trait Area {
    fn area(&self) -> u64;
}

impl Area for Rectangle {
    fn area(&self) -> u64 {
        self.long();
        self.width * self.length
    }
}

pub trait Long {
    fn long(&self);
}

impl Long for Rectangle {
    fn long(&self) {
        std::thread::sleep(std::time::Duration::from_secs(20));
    }
}


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

    #[test]
    fn it_works() {
        let r = Rectangle { width: 2, length: 3 };
        let result = r.area();
        assert_eq!(result, 6);
    }
}

examples/mock-long-running-trait/Cargo.toml

[package]
name = "area-struct-and-trait"
version = "0.1.0"
edition = "2021"

[dependencies]
mockall = "0.13.0"

examples/mock-long-running-trait/src/lib.rs

#![allow(dead_code)]


struct Rectangle {
    width: u64,
    length: u64,
}

pub trait Area {
    fn area(&self) -> u64;
}

impl Area for Rectangle {
    fn area(&self) -> u64 {
        self.long();
        self.width * self.length
    }
}

#[cfg(test)]
use mockall::{automock, predicate::*};
#[cfg_attr(test, automock)]
pub trait Long {
    fn long(&self);
}

impl Long for Rectangle {
    fn long(&self) {
        std::thread::sleep(std::time::Duration::from_secs(20));
    }
}


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

    #[test]
    fn it_works() {
        let mut mock = MockLong::new();
        mock.expect_long()
            .with()
            .returning(|| ());

        let r = Rectangle { width: 2, length: 3 };
        let result = r.area();
        assert_eq!(result, 6);
    }
}