Symfony\Component\Security\Authentication\Token\UsernamePasswordToken::eraseCredentials PHP Method

    public function eraseCredentials()
    {
        parent::eraseCredentials();
        $this->credentials = null;
    }

 public function testEraseCredentials()
 {
     $token = new UsernamePasswordToken('foo', 'bar');
     $token->eraseCredentials();
     $this->assertEquals('', $token->getCredentials());
 }