title: Mock is giving missing method exception in spock framewrok
body: <p>I am running my Junit test cases for my groovy class using spock framework I am using <code>Mock</code> to invoke my class. but it is giving me <code>MissingMethodException</code> but if I invoke the same method by normal creating object <code>def obj = new MyClass()</code> way it is working. please let me know am I missing something? below is my stacktrace</p>
  
  <pre><code>Expected no exception to be thrown, but got 'groovy.lang.MissingMethodException'
      at spock.lang.Specification.noExceptionThrown(Specification.java:119)
      at .AsplTest.fetchXmlTest(AsplTest.groovy:35)
  Caused by: groovy.lang.MissingMethodException: No signature of method: com.webservice.Service.fetchAsplXml() is applicable for argument types: (java.lang.String, groovy.net.xmlrpc.XMLRPCServerProxy, java.lang.String) values: [3c98fa0dd1b5d92af599779bfb7be655, groovy.net.xmlrpc.XMLRPCServerProxy@797b0699, ...]
  Possible solutions: getFetchAsplXml()
      at .AsplTest.fetchXmlTest(AsplTest.groovy:33)
  </code></pre>
  
  <p>below is my test code</p>
  
  <pre><code>public void fetchXmlTest() {
          given:
          def asplObject=Mock(Service);
          when:
          asplObject.fetchXml(sessionId, serverProxy, "https://serverproxy")
          then:
          noExceptionThrown()
      }
  </code></pre>
  
  <p>FYI:
  my groovy version is 2.4.12 and spock version 1.1-groovy-2.4</p>