Testing

Testing is fundamental to Rust.

Unit, integration, and documentation tests all come built-in.

Organizing Tests

Tests typically end up in 1 of 4 possible locations:

Immediately beside the functionality tested (Unit Tests)
In a tests submodule (Unit Tests)
In documentation. (Documentation Test)
In the tests/ directory. (Integration Tests)

Unit Tests

Allows testing functionality in the same module and environment.
Typically exist immediately near the functionality.
Good for testing to make sure a single action works.

Unit Tests

Allows testing as if the functionality is being used elsewhere in the project.
For testing private APIs and functionality.
Good for testing expected processes and use cases.

`tests` Submodule

#![allow(unused)]
fn main() {
enum Direction { North, South, East, West }

fn is_north(dir: Direction) -> bool {
    match dir {
        Direction::North => true,
        _ => false,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn is_north_works() {
        assert!(is_north(Direction::North) == true);
        assert!(is_north(Direction::South) == false);
    }
}
}

`tests` Submodule

$ cargo test
running 1 test
test tests::is_north_works ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured

Documentation Tests

Allows testing public functionality.
Is displayed in rustdoc output.
For demonstrating expected use cases and examples.

Documentation Tests

#![allow(unused)]
fn main() {
/// ```rust
/// use example::Direction;
/// let way_home = Direction::North;
/// ```
pub enum Direction { North, South, East, West }
}

Documentation Tests

$ cargo test
running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured

   Doc-tests example

running 1 test
test Direction_0 ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured

Integration Tests

Tests as if the crate is an external dependency.
Intended for longer or full-function tests.

Integration Tests

./tests/basic.rs

use example::{is_north, Direction};

#[test]
fn is_north_works() {
    assert!(is_north(Direction::North) == true);
    assert!(is_north(Direction::South) == false);
}

Integration Tests

$ cargo test
running 1 test
test is_north_works ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured

     Running target/debug/deps/example-9f39afa5d2a1c6bf

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured

   Doc-tests example

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured