Test::Scheduler

An implementation of the Perl 6 Scheduler role that uses virtualized time. This allows for testing of code depending on constructs like Promise.in(...) and Supply.interval(...) more quickly and reliably than would be possible if real time were used.

Synopsis

use Test;
use Test::Scheduler;

sub timeout($source, $timeout) {
    supply {
        whenever $source -> $value {
            state $values++;
            emit $value;

            my $last-values = $values;
            whenever Promise.in($timeout) {
                if $last-values == $values {
                    die "Timed out";
                }
            }
        }
    }
}

{
    my $*SCHEDULER = Test::Scheduler.new;
    my $test-source = supply {
        for 1, 2, 5 {
            whenever Promise.in($_) {
                emit 'badger';
            }
        }
    }
    my $timed-out = timeout($test-source, 2);
    my @received;
    my $died = False;
    $timed-out.tap:
        { @received.push($_) },
        quit => { $died = True }

    is @received, [], 'No values yet';

    $*SCHEDULER.advance-by(1);
    is @received, ['badger'], 'one value after 1s';
    nok $died, 'No timeout yet';

    $*SCHEDULER.advance-by(1);
    is @received, ['badger', 'badger'], 'Two value after 2s';
    nok $died, 'No timeout yet';

    $*SCHEDULER.advance-by(1);
    is @received, ['badger', 'badger'], 'Still two value after 3s';
    nok $died, 'Still not timed out yet';

    $*SCHEDULER.advance-by(1);
    is @received, ['badger', 'badger'], 'Still two value after 4s';
    ok $died, 'And have timed out';
}

done-testing;