Rust Essentials - Second Edition

The tests module

In a more realistic, larger project, tests are separated from the application code:

• Unit tests are collected in a module test
• Integration tests are collected in a lib.rs file in a tests directory

The code generated by Cargo for a library groups the tests inside a mod tests, a so-called module (see Chapter 8, Organizing Code and Macros; if you prefer, you can come back to this section after having read Chapter 8, Organizing Code and Macros and have a better understanding of modules).

In order to work with functions defined in the main code, we have to add the command use super::*;, which brings all these functions into the scope of the tests module:

pub fn double(n: i32) -> i32 { n * 2 } #[cfg(test)] mod tests { use super::*; ...