Functions can be tested by using these attributes:
#[test] marks a function as a unit test. The function must take zero
parameters and return nothing.#[should_panic] marks a function as a panicking test.// unit_test.rs
// Conditionally compile `main` only when the test-suite is *not* being run.
#[cfg(not(test))]
fn main() {
println!("If you see this, the tests were not compiled nor ran!");
}
// Conditionally compile the module `test` only when the test-suite is run.
#[cfg(test)]
mod test {
// A helper function `distance_test` will need.
fn distance(a: (f32, f32), b: (f32, f32)) -> f32 {
(
(b.0 - a.0).powi(2) +
(b.1 - a.1).powi(2)
).sqrt()
}
#[test]
fn distance_test() {
assert!(distance((0f32, 0f32), (1f32, 1f32)) == (2f32).sqrt());
}
#[test]
#[should_panic]
fn failing_test() {
assert!(1i32 == 2i32);
}
}
Tests can be run with cargo test or rustc --test.
$ rustc --test unit_test.rs
$ ./unit_test
running 2 tests
test test::distance_test ... ok
test test::failing_test ... ok
test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured
If --test were not included, then this would happen
$ rustc unit_test.rs
$ ./unit_test
If you see this, the tests were not compiled nor ran!
attributes, conditional compilation, and mod.