@Override
  public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
    throws BeansException {
    Assert.isInstanceOf(BeanDefinitionRegistry.class, beanFactory,
      "SpockMockPostprocessor can only be used on bean factories that "
        + "implement BeanDefinitionRegistry");
    postProcessBeanFactory(beanFactory, (BeanDefinitionRegistry)beanFactory);
  }
Create a new {@link SpockMockPostprocessor} instance with the given initial
definitions.

@param definitions the initial definitions
spock-spring/src/main/java/org/spockframework/spring/mock/SpockMockPostprocessor.java