Android unit test not moked

I followed this guide http://ift.tt/1zlzRtn and but i am stuck with this error

junit.framework.AssertionFailedError: Exception in constructor: testSaveJson (java.lang.RuntimeException: Method put in org.json.JSONObject not mocked. See http://ift.tt/1zlzRtn for details.

I added like the guide says but it doesn't make a difference

 testOptions { 
    unitTests.returnDefaultValues = true
  }