Macro faux::from_fn

macro_rules! from_fn {
    ($matcher:expr) => { ... };
}

Returns an ArgMatcher that succeeds if the provided closure returns true.

The returned Argmatcher implements fmt::Display using the string representation of the closure, so it is only recommended for use with simple closures. For complex argument matching, implement your own ArgMatcher to make the expectation message more specific and less verbose.

use faux::{from_fn, matcher::ArgMatcher};

let contains_hello = from_fn!(|message: &str| message.contains("hello"));
assert!(contains_hello.matches("hello world"));
assert!(!contains_hello.matches("bye world"));
println!("{}", contains_hello); // '|message: &str| message.contains("hello")'