Cargo

main.rs lib.rs other.rs another.rs

-lib.rs

pub mod other;
pub mod another; 

-main.rs

// Cargo.toml name="xxx"
use xxx::{...*...};

other.rs

//if use another.rs
use super::another...

about test

/tests/*.rs

use xxx::...

The lib.rs and main.rs files are two independent entry points for your package.

more

Read more: Clear explanation of Rust’s module system