getJson() public static method

Gets Json String of Object Patch
public static getJson ( ) : string
return string
 /**
  * @dataProvider mockProvider
  * @param Invoice $obj
  */
 public function testQrCode($obj, $mockApiContext)
 {
     $mockPayPalRestCall = $this->getMockBuilder('\\PayPal\\Transport\\PayPalRestCall')->disableOriginalConstructor()->getMock();
     $mockPayPalRestCall->expects($this->any())->method('execute')->will($this->returnValue(ImageTest::getJson()));
     $result = $obj->qrCode("invoiceId", array(), $mockApiContext, $mockPayPalRestCall);
     $this->assertNotNull($result);
 }