private void register(ConfigurableListableBeanFactory beanFactory,
                        BeanDefinitionRegistry registry, Definition definition) {
    if (definition instanceof MockDefinition) {
      registerMock(beanFactory, registry, (MockDefinition)definition);
    } else if (definition instanceof SpyDefinition) {
      registerSpy(beanFactory, registry, (SpyDefinition)definition);
    }
  }
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