private void registerAliases(ConfigurableListableBeanFactory beanFactory,
                               MockDefinition definition, String beanName) {
    for (String alias : definition.getAliases()) {
      beanFactory.registerAlias(beanName, alias);
    }
  }
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