private static Cluster mockBootstrapCluster() {
        return Cluster.bootstrap(ClientUtils.parseAndValidateAddresses(
                singletonList("localhost:8121"), ClientDnsLookup.USE_ALL_DNS_IPS));
    }
A unit test for KafkaAdminClient.

See AdminClientIntegrationTest for an integration test.
clients/src/test/java/org/apache/kafka/clients/admin/KafkaAdminClientTest.java