public function testTimerFunctionReceivesTimerSignature()
{
declare (ticks=1);
$clock = new Clock();
$clock->addPeriodicTimer(1, function ($signature) use($clock) {
$clock->clear($signature);
});
$start = microtime(true);
$clock->block();
$duration = microtime(true) - $start;
$this->assertGreaterThan(1, $duration);
$this->assertLessThan(1.001, $duration);
}