void assertZookeeperServerImplementation(String expectedClassName,
                                             ClusterControllerContainerCluster clusterControllerCluster) {
        for (ClusterControllerContainer c : clusterControllerCluster.getContainers()) {
            var builder = new ComponentsConfig.Builder();
            c.getConfig(builder);
            assertEquals(1, new ComponentsConfig(builder).components().stream()
                                                         .filter(component -> component.classId().equals(expectedClassName))
                                                         .count());
        }
    }
Here there is no good choice.
config-model/src/test/java/com/yahoo/vespa/model/content/ContentClusterTest.java