Doctrine\Tests\OXM\Marshaller\MarshallerTest::itShouldHandleCircularReferences PHP Method

    public function itShouldHandleCircularReferences()
    {
        $article = new Article();
        $article->name = 'article one';
        $tag = new Tag();
        $tag->name = 'oxm';
        $tag->article = $article;
        $tag2 = new Tag();
        $tag2->name = 'xml';
        $tag2->article = $article;
        $article->tags = array($tag, $tag2);
        $xml = $this->marshaller->marshalToString($article);
        $this->assertXmlStringEqualsXmlString('<?xml version="1.0" encoding="UTF-8"?>
            <article name="article one">
             <tag name="oxm" />
             <tag name="xml" />
            </article>', $xml);
        $otherArticle = $this->marshaller->unmarshalFromString($xml);
        $this->assertTrue($otherArticle instanceof Article);
        $this->assertEquals('article one', $otherArticle->name);
        $this->assertCount(2, $otherArticle->tags);
        $this->assertEquals('oxm', $otherArticle->tags[0]->name);
        $this->assertEquals('xml', $otherArticle->tags[1]->name);
        $article2 = new Article();
        $article2->name = 'article two';
        $tag3 = new Tag();
        $tag3->name = 'three';
        $tag3->article = $article2;
        $tag4 = new Tag();
        $tag4->name = 'four';
        $tag4->article = $article2;
        $article2->tags = array($tag3, $tag4);
        $xml = $this->marshaller->marshalToString($article2);
        $this->assertXmlStringEqualsXmlString('<?xml version="1.0" encoding="UTF-8"?>
            <article name="article two">
             <tag name="three" />
             <tag name="four" />
            </article>', $xml);
        $article2 = $this->marshaller->unmarshalFromString($xml);
        $this->assertTrue($article2 instanceof Article);
        $this->assertEquals('article two', $article2->name);
        $this->assertCount(2, $article2->tags);
        $this->assertEquals('three', $article2->tags[0]->name);
        $this->assertEquals('four', $article2->tags[1]->name);
        //        $this->assertEquals($article2, $article2->tags[1]->article);
        $tag4Article = new Article();
        $tag4Article->name = 'article for tag4';
        $tag4->article = $tag4Article;
        $xml = $this->marshaller->marshalToString($tag4);
        $this->assertXmlStringEqualsXmlString('<?xml version="1.0" encoding="UTF-8"?>
             <tag name="four">
                <article name="article for tag4" />
             </tag>', $xml);
        $otherTag4 = $this->marshaller->unmarshalFromString($xml);
        $this->assertTrue($otherTag4 instanceof Tag);
        $this->assertEquals('article for tag4', $otherTag4->article->name);
        $this->assertEquals('four', $otherTag4->name);
    }