public static Class<?>[] getCategoryAnnotations(Class<?> c) {
    Category category = c.getAnnotation(Category.class);
    if (category != null) {
      return category.value();
    }
    return new Class<?>[0];
  }
ClassFinder that is pre-configured with filters that will only allow test classes. The name is
strange because a logical name would start with "Test" and be confusing.
hbase-common/src/test/java/org/apache/hadoop/hbase/ClassTestFinder.java