You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: root_tests.rs
    path of file: ./repos/deep_causality/deep_causality/tests/types/context_types/node_types
    
    the code of the file until where you have to start completion: // SPDX-License-Identi
    
fn test_to_string() {
    let id = 1;

    let d = Root::new(id);
    assert_eq!(d.id(), id);

    let exp = format!("Root ID: {}", id);
    let act = d.to_string();
    assert_eq!(act, exp);
}