Grails controller unit tests for uploading a file

I want 'test first' developing grails controller. Until now the scaffolding produces integration tests and these tests are executed in a grails environment with all the injected methods and properties from grails like: request, flash, params and so on.

But for unit tests i have to mock that, because i want no dependencies of other components.

Glen Smith has described in his blog how to achieve that:
http://blogs.bytecode.com.au/glen/2008/03/12/mockfor-march---unit-testing-grails-controllers.html
So i created a AbstractControllerTestCase:

abstract class AbstractControllerTest extends GroovyTestCase {
 
     // ControllerTest's have to provide the controllerClass
     // def controllerClass
     def redirectParams
     def renderParams
     def params
     def controller
     def session
     def flash
     def message
 
     void setUp(){
          redirectParams= [:]
          params = [:]
          session = [:]
          flash = [:]
          renderParams = [:]    
          controllerClass.metaClass.redirect = { Map args -> redirectParams = args }
          controllerClass.metaClass.getParams = { -> params }
          controllerClass.metaClass.getSession = { -> session }  
          controllerClass.metaClass.getFlash = { -> flash }
          controllerClass.metaClass.message = { Map args -> message }
          controllerClass.metaClass.render = { Map args -> renderParams = args }  
     }
 
     void tearDown(){
          def remove = GroovySystem.metaClassRegistry.&removeMetaClass
          remove controllerClass
     }
   
}

To test a controller method that handle a file upload i need to mock also the request as multipart request. My solution was to use the 'propertyMissing(String name,Object arg)' method invocation hook. The controller use a request property, so i provide a mocked request.

Here is the test method (Uses Spring MockHttpServletRequest):

   void testImportToCSWFileIsEmpty(){
       MockMultipartHttpServletRequest request = new MockMultipartHttpServletRequest()
       request.addFile(new MockMultipartFile("xmlFile"))
       MetadataController.metaClass.propertyMissing << { String name, Object args -> 
          request
       }
       params.cswUrl = "http://mockedCsw"
       controller.importToCSW()   
       assertEquals("metadata.import.csw.fileempty",flash.message)
   }

Are there easier ways ?