add rule calls to junit setup/teardown only once, there might be several test mixins applied for the same class
use FieldExpression instead of VariableExpression
Add ExpandoMetaClass.enableGlobally() to static initializer of test classes that use mixins
use GrailsMetaClassUtils.getExpandoMetaClass / GrailsMetaClassUtils.getMetaClass to get metaclass
- tests might load some instances with the ordinary MetaClassImpl instead of ExpandoMetaClass