if (log.isDebugEnabled())
and found that clover is capable of doing that, but as we're using Maven 2, the maven clover plugin doesn't seem to support it now, believe me, I've reviewed their source code.
Finally I found a solution that does the trick. In your test case, just set the logging level of the class under test to whatever you want, test your class and then set the logging level back! e.g. your class is foo.bar.MyClass
Logger logger = Logger.getLogger("foo.bar");
Level oldLevel = logger.getLevel();
logger.setLevel(Level.OFF);
// test your class here...
logger.setLevel(oldLevel);