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

It's possible to construct tests based on arbitrarily complex parameters and any information known at build time (including anything you can load from a file) with a build script.

We tell Cargo where the build script is:

Cargo.toml

[package]
name = "test"
version = "0.1.0"
build = "build.rs"

In the build script, we generate our test logic and place it in a file using the environment variable OUT_DIR:

build.rs

fn main() {
    let out_dir = std::env::var("OUT_DIR").unwrap();
    let destination = std::path::Path::new(&out_dir).join("test.rs");
    let mut f = std::fs::File::create(&destination).unwrap();

    let params = &["abc", "fooboo"];
    for p in params {
        use std::io::Write;
        write!(
            f,
            "
#[test]
fn {name}() {{
    assert!(true);
}}",
            name = p
        ).unwrap();
    }
}

Finally, we create a file in our tests directory that includes the code of the generated file.

tests/generated_test.rs

include!(concat!(env!("OUT_DIR"), "/test.rs"));

That's it. Let's verify that the tests are run:

$ cargo test
   Compiling test v0.1.0 (...)
    Finished debug [unoptimized + debuginfo] target(s) in 0.26 secs
     Running target/debug/deps/generated_test-ce82d068f4ceb10d

running 2 tests
test abc ... ok
test fooboo ... ok