/**
  * @param string $messageName
  * @param array $parameters Parameters with value === `null` will be filtered out.
  */
 private function write($messageName, array $parameters)
 {
     /** @noinspection AdditionOperationOnArraysInspection */
     $parameters = ['timestamp' => Util::formatTimestamp(), 'flowId' => $this->flowId] + $parameters;
     // Filter out optional parameters.
     $parameters = array_filter($parameters, function ($value) {
         return $value !== null;
     });
     $this->writer->write(Util::format($messageName, $parameters));
 }
 public function testFormatTimestampNow()
 {
     $now = new DateTime();
     $result = Util::formatTimestamp();
     self::assertEquals($now, new DateTime($result), '', 1.0);
 }