ConfigurationProperties with constructor binding cannot be mocked

[sdeleuze]

I have migrated https://spring.io/guides/tutorials/spring-boot-kotlin/ to Spring Boot 2.2.0.RELEASE and updated it to leverage immutable configuration properties. As discussed with @snicoll, @ConfigurationProperties are not scanned by default in test slices, so I have to add to my @WebMvcTest test either @EnableConfigurationProperties(BlogProperties::class) or mock BlogProperties bean.

My test works with @EnableConfigurationProperties(BlogProperties::class) but fails if I try to mockk BlogProperties bean (in my case with @MockkBean from https://github.com/Ninja-Squad/springmockk) with following error:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.example.blog.BlogProperties#0': @EnableConfigurationProperties or @ConfigurationPropertiesScan must be used to add @ConstructorBinding type com.example.blog.BlogProperties

[snicoll]

Interesting data point is that it only fails if @ConstructorBinding is set on the type. If the annotation is set on the constructor, then the error goes away. I have a hunch that this is directly related to #18685

[snicoll]

And I was wrong. It works because the mock does not expose the annotations that are available on the target constructor so the current validation does not apply.

[philwebb]

@sdeleuze Have you got a branch somewhere we can look at?

[snicoll]

@philwebb that wasn't obvious from my previous comment but that's not Kotlin specific as far as I can see. I didn't try with Kotlin so can't say but that's what seems to happen with plain Java, see https://github.com/snicoll-scratches/test-mock-config-props

If the annotation is found in both cases, it will fail in both cases whereas this issue is about it not failing at all. If a bean is mocked, the verification should not check for the bind method anyway.

[sdeleuze]

@philwebb Sadly not anymore, it was on my laptop which was stolen last week.

[philwebb]

:(

[davinkevin]

Same thing for me with mockito btw (in kotlin too, not tested in java).

https://gitlab.com/davinkevin/Podcast-Server/issues/37