Mocking out the logger

I have a simple CachingService that is a wrapper for Ehcache.   I wanted to create a unit test out of CachingService, since it doesn't have any dependencies.  However after running the test I was getting an error:  "groovy.lang.MissingPropertyException:  No such property: log for class:  CacheService".

Oops I forgot I have some logging inside my CachingService class.   At runtime Grails auto-magically injects a "log" property into service classes.  If my test was an integration test then there wouldn't be a problem.   So I have two options, either mock out the logger or run my test as an integration tests.   I decided to mock out the logger, which required me to do the following:

1.  Create a MockLogger class (primarily since I will probably have to mock out the logger in other classes in the future)

class MockLogger {

  void info(message) {}

  void warn(message) {}

  void debug(message) {}

  void error(message) {}

}

2.  Inject my MockLogger as a property named "log" via getLog() into my service class via ExpandoMetaClass

void setUp() {

  CachingService.metaClass.getLog = { -> new MockLogger() }

}

3.  Reset the state of CachingService before dynamically adding the property "log"

void tearDown() {

  def remove = GroovySystem.metaClassRegistry.&removeMetaClass

  remove CachingService

}

There may be other ways to mock out the logger, but this approach seemed simple enough.  Do you have an easier approach?  If so please drop a comment.