Sokil\Mongo\ExpressionTest::testWhereFieldExists PHP Method

    public function testWhereFieldExists()
    {
        // create new document
        $document = $this->collection->createDocument(array('fieldName' => '1'));
        $document->save();
        $documentId = $document->getId();
        // scalar value
        $this->assertEmpty($this->collection->find()->whereExists('unexistedFieldName')->findOne());
        $this->assertEquals($documentId, $this->collection->find()->whereExists('fieldName')->findOne()->getId());
    }