Crate repeated_assert

An assertion macro that tries to assert expressions multiple times

repeated_assert! re-tries to assert expressions until either all expressions are true or the maximum amount of repetitions has been reached. The current thread will be blocked between tries.

This is useful when waiting for events from another thread (or process). Waiting for a short time might result in a failing test, while waiting too long is a waste of time.

Examples

Waiting for a file to appear (re-try up to 10 times, wait 50 ms between tries)

repeated_assert!{ 10, Duration::from_millis(50);
    if Path::new("should_appear_soon.txt").exists();
};

Waiting for variable x to equal 3

repeated_assert!{ 10, Duration::from_millis(50);
    eq x, 3;
};

Multiple assertions

repeated_assert!{ 10, Duration::from_millis(50);
    if Path::new("should_appear_soon.txt").exists();
    eq x, 3;
};

Temporary variables

repeated_assert!{ 10, Duration::from_millis(50);
    let checksum = crc("file_is_being_written.txt");
    eq checksum, 1234;
};

Catch failing tests

It's also possible to "catch" failing tests by executing some code if the expressions couldn't be asserted in order to trigger an alternate strategy. This can be useful if the tested program relies on an unreliable service. This counters the idea of a test to some degree, so use it only if the unreliable service is not critical for your program.

Poke unreliable service after 5 unsuccessful assertion attempts

repeated_assert!{ 10, Duration::from_millis(50), 5, {
        // poke unreliable service
    };
    if Path::new("should_appear_soon.txt").exists();
};

Macros

repeated_assert