Macro k9::assert_err_matches_regex

macro_rules! assert_err_matches_regex {
    ($err:expr, $regex:expr) => { ... };
    ($s:expr, $regex:expr, $context:expr) => { ... };
}

Asserts that the passed Result argument is an Err and and the debug string of that error matches provided regex. Regular expressions are compiled using regex crate.

use k9::assert_err_matches_regex;
// Borrowed from Rust by Example: https://doc.rust-lang.org/stable/rust-by-example/std/result.html
fn divide(x: f64, y: f64) -> Result<f64, &'static str> {
    if y == 0.0 {
        // This operation would `fail`, instead let's return the reason of
        // the failure wrapped in `Err`
        Err("Cannot divide by 0.")
    } else {
        // This operation is valid, return the result wrapped in `Ok`
        Ok(x / y)
    }
}
let division_error = divide(4.0, 0.0);
assert_err_matches_regex!(division_error, "Cannot");