public function testGetSetMetadata()
{
$document = new Document();
$this->assertSame(null, $document->getMetadata('foo'));
$this->assertSame('default', $document->getMetadata('foo', 'default'));
$document->setMetadata('foo', 'bar');
$this->assertSame('bar', $document->getMetadata('foo'));
$this->assertSame('bar', $document->getMetadata('foo', 'default'));
}