Tests

In Perl, we put our tests in a t directory and then prove -l will run them. Similarly, Rust has a tests directory and cargo test will run the tests there.

But Rust does this mostly for integration tests. Unit tests are typically put right in the same file as the code.

For example, I wrote a Perl module called Time::Moment::Epoch which converts a bunch of different epoch times to Time::Moment times. It has a bunch of unit tests in t/Time-Moment-Epoch.t.

I wrote a similar Rust crate called epochs, which converts those same epoch times to chrono::NaiveDateTime times. It has similar unit tests at the bottom of the library file itself.

The #[cfg(test)] macro tells cargo to run those tests when it is called as cargo test, but to ignore them when it is called as cargo build or cargo run.

Update (2024-05-15): I talked about testing at the Rust & C++ Cardiff book club. We are reading Rust for Rustaceans together and I did chapter 6. You can view my slides, some of which have links that I did not follow during the talk.