assertLinkByHref example

// Set the formatter to link to the entity.     $this->display->setComponent($this->fieldName, [
      'type' => 'string',
      'settings' => [
        'link_to_entity' => TRUE,
      ],
    ]);
    $this->display->save();

    $this->renderEntityFields($entity, $this->display);
    $this->assertLink($value, 0);
    $this->assertLinkByHref($entity->toUrl()->toString());

    // $entity->toUrl('revision') falls back to the canonical URL if this is no     // revision.     $this->assertLinkByHref($entity->toUrl('revision')->toString());

    // Make the entity a new revision.     $old_revision_id = $entity->getRevisionId();
    $entity->setNewRevision(TRUE);
    $value2 = $this->randomMachineName();
    $entity->{$this->fieldName}->value = $value2;
    $entity->save();