Unit test withFilters not working for grails 2.0.0.RC1

class AuthenticationFilters {
  def filters = {
    create(controller:'openAm', action:'create') {
      before = {
        if (params.username == '') {
          render (status: HttpServletResponse.SC_BAD_REQUEST) 
  	  return false
        }
    }
}

@TestMixin(GrailsUnitTestMixin)
@TestFor(OpenAmController)
@Mock (AuthenticationFilters)
class OpenAmControllerTests {
  @Test
  void testCreateActionIsFiltered() {
	withFilters(action: "create") {
	  println 'hello'
          controller.params.username = ''
	  controller.create()
			
	}
	assert  400 == response.status 
   }
}