As I would like each test to be independent from the other tests each one need its own configuration. (e.g. a different database or a different temporary folder).

One way to pass this information is by setting environment variables - but those are per process and thus I had to set the test to run in a single thread. How can I pass some parameter to each test?

The simplified version of the main file looks like this:

#[launch]
fn rocket() -> _ {
    rocket::build()
        .mount(
            "/",
            routes![
                main,
            ],
        )
        .attach(AdHoc::config::<MyConfig>())
}

The pseudo version of the test looks like this

#[test]
fn test_simple() {
    let rocket_toml_path = some_temporary_place();
    let database_name = random_for_this_test();
    save_rocket_toml with database_name in rocket_toml_path;

    std::env::set_var("ROCKET_CONFIG", rocket_toml_path);

     let client = Client::tracked(super::rocket()).unwrap();
     ...
}

The real code is in this repository in src/main.rs and src/test_simpl.rs