use Once;
static INIT: Once = new;
/// Initializes the test environment.
/// Guarantees that any global state (like loggers or environment variables)
/// is only set up once per test run, avoiding race conditions in multithreaded tests.
/// Helper function to temporarily set an environment variable for testing
/// and restore it afterward (though env::set_var in multithreaded tests
/// should be used carefully, it's fine for simple isolated integration tests).