unit test & integration test in Rust

integration_test.rs

// tests/integration_test.rs

use adder;

mod common;

#[test]
fn add_two_test() {
    common::setup();
    assert_eq!(adder::add_two(2), 4);
}

lib.rs

// src/lib.rs

pub fn add_two(a: i32) -> i32 {
    a + 2
}

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

    #[test]
    fn add_two_unit_test() {
        assert_eq!(add_two(2), 4);
    }
}

mod.rs

// tests/common/mod.rs

fn add_two_unit_test() {
    assert!(add_two(2) == 4);
}