Macro assert_step_err 

macro_rules! assert_step_err {
    ($expr:expr $(,)?) => { ... };
    ($expr:expr, $msg:expr $(,)?) => { ... };
}

Assert that a Result is Err and unwrap the error.

Optionally asserts that the error’s display contains a substring.

Note: The (expr, "substring") form requires the error type to implement std::fmt::Display so it can be converted to a string for matching.

Examples

use rstest_bdd::assert_step_err;

let err: Result<(), &str> = Err("boom");
let e = assert_step_err!(err, "boom");
assert_eq!(e, "boom");

Single-argument form:

use rstest_bdd::assert_step_err;

let err: Result<(), &str> = Err("boom");
let e = assert_step_err!(err);
assert_eq!(e, "boom");