public function testLinkClass()
 {
     $this->assertEquals('', $this->attributeMetadata->getLinkClass());
     $newAttributeMetadata = $this->attributeMetadata->withLinkClass('class');
     $this->assertEquals('class', $newAttributeMetadata->getLinkClass());
     $this->assertNotEquals($this->attributeMetadata, $newAttributeMetadata);
 }