Macro assert_err_eq 

macro_rules! assert_err_eq {
    ($result:expr, $expected:expr) => { ... };
}

Asserts that a result is an error and contains a specific tag or message.

This macro iterates through the error’s core message and all attached contexts (both simple and grouped) to find a match with the expected string.

Arguments

• $result - A Result or ComposableResult to check.
• $expected - The string to search for in tags, messages, or the core error.

Panics

Panics if the result is Ok or if the error does not contain the expected string.