public function testGetAndSetExtensionRegistry()
{
$mock = $this->getMock('Protobuf\\Extension\\ExtensionRegistry');
$registry = $this->configuration->getExtensionRegistry();
$this->assertInstanceOf('Protobuf\\Extension\\ExtensionRegistry', $registry);
$this->assertSame($registry, $this->configuration->getExtensionRegistry());
$this->configuration->setExtensionRegistry($mock);
$this->assertSame($mock, $this->configuration->getExtensionRegistry());
}