Test clone++ a content entity.
File
- 
              tests/src/ Functional/ EntityCloneContentRecursiveCircularTest.php, line 157 
Class
- EntityCloneContentRecursiveCircularTest
- Create a content and test a clone.
Namespace
Drupal\Tests\entity_clone\FunctionalCode
public function testContentWithTwoSameEntityReference() {
    $child_node1_title = $this->randomMachineName(8);
    $child_node1 = Node::create([
        'type' => 'test_content_type',
        'title' => $child_node1_title,
    ]);
    $child_node1->save();
    $parent_node_title = $this->randomMachineName(8);
    $parent_node = Node::create([
        'type' => 'test_content_type',
        'title' => $parent_node_title,
        'test_field_reference' => $child_node1,
        'test_another_field_reference' => $child_node1,
    ]);
    $parent_node->save();
    $settings = [
        'node' => [
            'default_value' => 0,
            'disable' => 0,
            'hidden' => 0,
        ],
    ];
    \Drupal::service('config.factory')->getEditable('entity_clone.settings')
        ->set('form_settings', $settings)
        ->save();
    $this->drupalGet('entity_clone/node/' . $parent_node->id());
    $this->submitForm([], $this->t('Clone'));
    $nodes = \Drupal::entityTypeManager()->getStorage('node')
        ->loadByProperties([
        'title' => $parent_node_title . ' - Cloned',
    ]);
    
    /** @var \Drupal\node\Entity\Node $parent_node_cloned */
    $parent_node_cloned = reset($nodes);
    $this->drupalGet('node/' . $parent_node_cloned->id());
    $first_reference = $parent_node_cloned->get('test_field_reference')
        ->first()
        ->get('entity')
        ->getTarget()
        ->getValue();
    $second_reference = $parent_node_cloned->get('test_another_field_reference')
        ->first()
        ->get('entity')
        ->getTarget()
        ->getValue();
    $this->assertEquals($child_node1->id(), $first_reference->id(), "Entity referenced twice time is correctly reused.");
    $this->assertEquals($child_node1->id(), $second_reference->id(), "Entity referenced twice time is correctly reused.");
}