Sharing dynamic state between #[test]s

Question

How do I share state between tests, short of storing it externally (e.g. environment variables, file, etc)?

Stainless has a setup macro thing named before_each, and I'm thinking of a similar thing, say shared_values, but whose variables would be accessible to all tests, and which would also be ran once (at the beginning of the test suite).

Answer 1

There's nothing special about tests. They are "just" functions that run in multiple threads. Therefore, one solution is do the same thing you would in other code: create a global mutable singleton:

use once_cell::sync::Lazy; // 1.5.2

static DATABASE: Lazy<String> = Lazy::new(|| format!("{} {}", "This was", "expensive"));

#[test]
fn one() {
    println!("{}", *DATABASE);
}

#[test]
fn two() {
    println!("{}", *DATABASE);
}

The test framework provides no hooks for an "after" callback, so there is no nice avenue to clean up this resource. Drop will not be called for singleton variables either.