public function testSubject()
{
$subjectA = $this->getMock('\\stdClass');
$subjectB = $this->getMock('\\stdClass');
$payload = new Payload('id', $subjectA);
$this->assertSame($subjectA, $payload->getSubject());
$payload->setSubject($subjectB);
$this->assertSame($subjectB, $payload->getSubject());
}