How can I create parameterized tests in Rust?

Question

I want to write test cases that depend on parameters. My test case should be executed for each parameter and I want to see whether it succeeds or fails for each parameter.

Answer 1

My rstest crate mimics pytest syntax and provides a lot of flexibility. A Fibonacci example can be very neat:

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

    use rstest::rstest;

    #[rstest(input, expected,
    case(0, 0),
    case(1, 1),
    case(2, 1),
    case(3, 2),
    case(4, 3),
    case(5, 5),
    case(6, 8)
    )]
    fn fibonacci_test(input: u32, expected: u32) {
        assert_eq!(expected, fibonacci(input))
    }
}

pub fn fibonacci(input: u32) -> u32 {
    match input {
        0 => 0,
        1 => 1,
        n => fibonacci(n - 2) + fibonacci(n - 1)
    }
}

Output:

/home/michele/.cargo/bin/cargo test
   Compiling fib_test v0.1.0 (file:///home/michele/learning/rust/fib_test)
    Finished dev [unoptimized + debuginfo] target(s) in 0.92s
     Running target/debug/deps/fib_test-56ca7b46190fda35

running 7 tests
test test::fibonacci_test::case_1 ... ok
test test::fibonacci_test::case_2 ... ok
test test::fibonacci_test::case_3 ... ok
test test::fibonacci_test::case_5 ... ok
test test::fibonacci_test_case_6 ... ok
test test::fibonacci_test::case_4 ... ok
test test::fibonacci_test::case_7 ... ok

test result: ok. 7 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

Every case is run as a single test case.

The syntax is simple and neat and, if you need, you can use any Rust expression as the value in the case argument.

rstest also supports generics and pytest-like fixtures.

---

Don't forget to add rstest to dev-dependencies in Cargo.toml.