Add support for JUnit 5 extension.

[NeveHanter]

Currently spring-kafka allow using KafkaEmbedded using @ClassRule or using spring's injection thanks to provided context customizer.

Is there any reason why there's no JUnit 5 extension provided or are there any plans on supporting this?

For now I'm using custom written JUnit 5 extension which implements both replication manager shutdown and high watermark hacks from #194 but it will be best to have this done properly by spring-kafka itself.

[garyrussell]

We didn't write a JUnit5 extension because we already have the @EmbeddedKafka annotation, which can be used with JUnit5.

Documentation here.

Feel free to create a PR for your extension and we'll consider merging it if it adds significant value.

[Woodham]

@garyrussell As far as I can see, the @EmbeddedKafka still requires junit4 (or junit-jupiter-vintage) on the classpath because KafkaEmbedded.java imports org.junit.rules.ExternalResource.

Is there any way to use KafkaEmbedded without having junit 4 on the classpath?

[artembilan]

Yep! That's good catch, indeed!

I think we need a JUnit 5 variant of the KafkaEmbedded and that @EmbeddedKafka should be able to select the proper implementation according classpath state.
Although we definitely should extract a common logic in the separate class, free from JUnit at all and provide appropriate wrappers.
Something like KafkaEmbeddedJunit4Rule and KafkaEmbeddedJunit5Extension ?