assertItemsTableCount example

$definition = \Drupal::entityTypeManager()->getDefinition($entity_type);
    $user = User::create(['name' => 'test name']);
    $user->save();
    /** @var \Drupal\entity_test_revlog\Entity\EntityTestMulWithRevisionLog $entity */
    $entity = EntityTestMulWithRevisionLog::create([
      'type' => $entity_type,
    ]);

    // Save the entity, this creates the first revision.     $entity->save();
    $revision_ids[] = $entity->getRevisionId();
    $this->assertItemsTableCount(1, $definition);

    // Create the second revision.     $entity->setNewRevision(TRUE);
    $random_timestamp = rand(1e8, 2e8);
    $this->createRevision($entity, $user, $random_timestamp, 'This is my log message');

    $revision_id = $entity->getRevisionId();
    $revision_ids[] = $revision_id;

    $storage = \Drupal::entityTypeManager()->getStorage('entity_test_mul_revlog');
    $entity = $storage->loadRevision($revision_id);