public function testAttributesAreImmutableAndRemoveable()
{
$this->assertNull($this->server->getAttribute('foo'));
$server = $this->server->withAttribute('foo', 'bar');
$this->assertNotSame($this->server, $server);
$this->assertEquals('bar', $server->getAttribute('foo'));
$server2 = $server->withoutAttribute('foo');
$this->assertNotSame($server, $server2);
$this->assertNotSame($server2, $server2->withoutAttribute('foo'));
$this->assertNull($server2->getAttribute('foo'));
}
