Sonata：如何以编程方式创建块？

Question

I am working on an application that uses Sonata's block bundle and Symfony 3.3.

I want to run some tests against a block service. That means programmatically creating and populating a block. Here is what I have so far in my fixture-generation class:

public function load(ObjectManager $manager)
{
    $siteRepository = $manager->getRepository('ApplicationSonataPageBundle:Site');
    $defaultSite = $siteRepository->findOneBy(['name'=>'vagrant.dev']);

    $page = new Page();
    $page->setName('An empty page');
    $page->setEnabled(true);
    $page->setTemplateCode('default');
    $page->setPosition(1);
    $page->setSite($defaultSite);
    $textBlockService = $this->getContainer()->get('app.block.text');

    //What goes here?

    $manager->persist($page);
    $manager->flush();
}

... and as you can see, I have a "what goes here?" area that I don't know how to populate.

app.block.text in the code sample above represents a text block service.

What exactly should I be doing to create and populate a block, now that I have access to a block service?