Solr Bundle should not rely on ezpublish-kernel integration tests to test features strictly related to Solr. Given that now we support for ezpublish-kernel:7.5 both Solr 6.6 and 7.7, this becomes more pressing matter. To add some integration test for Solr feature, a PR for Kernel is needed, which is a maintenance issue (e.g. impossible to have green CI just before merging, a need to keep compatibility with all supported versions of Solr).
Integration tests should be independent, the same way as in case of the ezplatform-richtext package. We might need some common package for common tests, but the goal here is to start on integration test setup dedicated for Solr.