Function mocktopus::mocking_utils::as_mut

pub unsafe fn as_mut<T>(t_ref: &T) -> &mut T

Converts non-mutable reference to a mutable one

Allows creating multiple mutable references to a single item breaking Rust's safety policy.

Safety

Use with extreme caution, may cause all sorts of mutability related undefined behaviors!

One safe use case is when mocking function, which gets called only once during whole test execution, for example:

#[mockable]
fn get_string(context: &mut Context) -> &mut String {
    context.get_mut_string()
}

#[test]
fn get_string_test() {
    let mocked = "mocked".to_string();
    unsafe {
        // MockResult::Return(&mut string) would fail
        get_string.mock_raw(|_| MockResult::Return(as_mut(&mocked)));
    }

    assert_eq!("mocked", get_string(&mut Context::default()));
}