<?php

namespace Drupal\Tests\drupalcon\Kernel;

use Drupal\drupalcon\Repository\ArticleRepository;
use Drupal\KernelTests\Core\Entity\EntityKernelTestBase;
use Drupal\node\NodeInterface;
use Drupal\Tests\node\Traits\NodeCreationTrait;

class ArticleRepositoryTest extends EntityKernelTestBase {

  use NodeCreationTrait;

  public static $modules = [
    'drupalcon',
    'node',
  ];

  /** @test */
  public function it_returns_blog_posts() {
// start test
    $this->createNode([
      'title' => 'Test post',
      'type' => 'article',
    ]);

    $repository = $this->container->get(ArticleRepository::class);

    $articles = $repository->getAll();

    $this->assertCount(1, $articles);
    $this->assertIsObject($articles[1]);

    $this->assertInstanceOf(NodeInterface::class, $articles[1]);
    $this->assertSame('article', $articles[1]->bundle());
    $this->assertSame('Test post', $articles[1]->label());
// end test
  }

}

---

Article Repository (Drupal\Tests\drupalcon\Kernel\ArticleRepository)
 ✔ It returns blog posts

Time: 00:00.449, Memory: 6.00 MB

OK (1 test, 15 assertions)