code: static void register(BeanDefinitionRegistry registry,
                         Set<Definition> definitions) {
      register(registry, SpockMockPostprocessor.class, definitions);
    }
docs: Register the processor with a {@link BeanDefinitionRegistry}. Not required when
  using the Spocks {@link spock.lang.Specification} as registration is automatic.
  
  @param registry the bean definition registry
  @param definitions the initial mock/spy definitions