PhpOffice\PhpPresentation\PhpPresentation::addExternalSlide PHP Method

    public function addExternalSlide(Slide $slide)
    {
        $slide->rebindParent($this);
        return $this->addSlide($slide);
    }

 /**
  * Test add external slide
  */
 public function testAddExternalSlide()
 {
     $origin = new PhpPresentation();
     $slide = $origin->getSlide();
     $object = new PhpPresentation();
     $object->addExternalSlide($slide);
     $this->assertEquals(2, $object->getSlideCount());
 }