Crate repeated_assert[][src]

Run assertions multiple times

This crate currently requires the nightly version of the Rust compiler.

repeated_assert runs assertions until they either pass 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.


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

repeated_assert::that(10, Duration::from_millis(50), || {

Waiting for variable x to equal 3

repeated_assert::that(10, Duration::from_millis(50), || {
    assert_eq!(x, 3);

Temporary variables

repeated_assert::that(10, Duration::from_millis(50), || {
    let checksum = crc("should_appear_soon.txt");
    assert_eq!(checksum, 1234);

Return result

repeated_assert::that(10, Duration::from_millis(50), || -> Result<_, Box<dyn std::error::Error>> {
    let checksum = crc("should_appear_soon.txt")?;
    assert_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::with_catch(10, Duration::from_millis(50), 5,
    || {
        // poke unreliable service
    || {



An assertion macro that tries to assert expressions multiple times



Run the provided function assert up to repetitions times with a delay in between tries.


Run the provided function assert up to repetitions times with a delay in between tries. Execute the provided function catch after repetitions_catch failed tries in order to trigger an alternate strategy.