Please, see `IntegrationConfigurationTests`.
`IntegrationConfigurationClassPostProcessor` is registered automatically by parsing first tag from any SI namespace.
But as you there is one more - `<component-scan>`, who register `ConfigurationClassPostProcessor` from SPR.
And the reason of our own, to register and process `@Configuration` if there is even no `<component-scan>` in the AC.
From other side `ConfigurationClassPostProcessor` from SPR may process our `@Configuration` and there is no reason to do it twice. That's why I added a check for `CoreIntegrationConfiguration` bean