Sokil\Mongo\Document::push PHP Method

    public function push($fieldName, $value)
    {
        $oldValue = $this->get($fieldName);
        // check if old value is list or sub document
        // on sub document throw exception
        if (is_array($oldValue)) {
            $isSubDocument = array_keys($oldValue) !== range(0, count($oldValue) - 1);
            if ($isSubDocument) {
                throw new InvalidOperationException(sprintf('The field "%s" must be an array but is of type Object', $fieldName));
            }
        }
        // prepare new value
        $value = Structure::prepareToStore($value);
        // field not exists
        if (!$oldValue) {
            if ($this->getId()) {
                $this->operator->push($fieldName, $value);
            }
            $value = array($value);
        } elseif (!is_array($oldValue)) {
            $value = array_merge((array) $oldValue, array($value));
            if ($this->getId()) {
                $this->operator->set($fieldName, $value);
            }
        } else {
            if ($this->getId()) {
                // check if array because previous $set operation on single value was executed
                $setValue = $this->operator->get('$set', $fieldName);
                if ($setValue) {
                    $setValue[] = $value;
                    $this->operator->set($fieldName, $setValue);
                } else {
                    $this->operator->push($fieldName, $value);
                }
            }
            $value = array_merge($oldValue, array($value));
        }
        // update local data
        parent::set($fieldName, $value);
        return $this;
    }

 public function testPushInvalidEmbeddedDocument()
 {
     $document = new Document($this->collection);
     try {
         $document->push('profiles', new ProfileDocument(array('name' => null)));
         $this->fail('InvalidDocumentException must be thrown, but method call was successfull');
     } catch (InvalidDocumentException $e) {
         $this->assertSame(array('name' => array('required' => 'REQUIRED_FIELD_EMPTY_MESSAGE')), $e->getDocument()->getErrors());
     }
 }