Testing #

This guide covers how to write and organize tests in Doing. Tests live alongside the code they test, in a #[cfg(test)] module at the bottom of each source file.

The goal is to test meaningful behavior without over-testing trivial code. When in doubt, focus on logic that could break—transformations, edge cases, and complex calculations.

Running Tests #

mise run test                  # Run all tests with coverage
mise run test -- --filter xyz  # Run tests matching "xyz"

# Without mise:
./tasks/test/build

What to Test #

Test:

• Methods with logic (arithmetic, transformations, conditionals)
• Display/formatting implementations
• Custom PartialEq/PartialOrd implementations
• Edge cases and boundary conditions
• Inverse operations (roundtrip tests)

Skip:

• Simple constructors that just assign fields
• Trivial getters that return field values
• From implementations that only call Self::new()

Before writing a test, ask: "Does this test verify actual logic, or just that Rust's field assignment works?"

Test Structure #

Tests are organized as nested modules within each source file:

#[cfg(test)]
mod test {
    use super::*;

    mod method_name {
        use pretty_assertions::assert_eq;

        use super::*;

        #[test]
        fn it_returns_expected_value() {
            let input = SomeType::new(42);

            assert_eq!(input.value(), 42);
        }
    }
}

Conventions #

Naming: Test functions use the pattern it_<does_something>. Module names match the method being tested.

Ordering: Test modules follow code style ordering - associated functions first (alphabetically), then methods (alphabetically).

Test body structure: Separate setup from assertions with a blank line. For tests with multiple assertion groups, separate each group with a blank line:

#[test]
fn it_handles_multiple_cases() {
    let foo = "foo";
    let bar = "bar";

    assert_ne!(foo, bar);

    let baz = "baz";

    assert_ne!(foo, baz);
}

Assertions: Use pretty_assertions for assert_eq! and assert_ne!:

use pretty_assertions::assert_eq;