rust-passert

Pretty/Power assertion macros for rust

Overview

An assert macro in the spirit of [Spock/Groovy assertions] (http://docs.groovy-lang.org/latest/html/documentation/core-testing-guide.html#_power_assertions) which evaluates and prints subexpressions, simplifying failure analysis

Example

#![feature(plugin)]
#![plugin(passert_macros)]

extern crate passert;

#[test]
#[should_panic]
fn it_works() {
    let a = 3;
    let b = 4;
    passert!(a + 2 + 3 == -b);
}

Output

running 1 test
Assertion failed:
a + 2 + 3 == -b
| |   |   |  ||
3 5   8   |  |4
          |  -4
          false
thread 'it_works' panicked at 'Assertion failed: a + 2 + 3 == -b', src/lib.rs:11

Limitations/Caveats

• All displayed subexpressions must implement Debug.
• The transformation of subexpression to strings via Debug is done after the whole expression has been evaluated. In cases where other subexpressions cause changes to previously evaluated subexpression the displayed value may be incorrect.
• The logical expressions && and || are not evaluated lazily.
• A new binding is created for each subexpression, this may have unintended side effects.