Macro assert_writeable_parts_eq

macro_rules! assert_writeable_parts_eq {
    ($actual_writeable:expr, $expected_str:expr, $expected_parts:expr $(,)?) => { ... };
    ($actual_writeable:expr, $expected_str:expr, $expected_parts:expr, $($arg:tt)+) => { ... };
}

See assert_writeable_eq.