We pass `null` for the class name here:

https://github.com/elastic/elasticsearch/blob/f086dd18ddc705bf84a1ff99d35196ec2498fd52/server/src/main/java/org/elasticsearch/plugins/PluginDescriptor.java#L261

However the class name is mandatory for the transport protocol today:

https://github.com/elastic/elasticsearch/blob/f086dd18ddc705bf84a1ff99d35196ec2498fd52/server/src/main/java/org/elasticsearch/plugins/PluginDescriptor.java#L156

This prevents various APIs from working in a cluster with stable plugins installed.
x-pack/plugin/security/src/test/java/org/elasticsearch/test/SecurityIntegTestCase.java
import org.elasticsearch.index.Index;
import org.elasticsearch.license.LicenseSettings;
import org.elasticsearch.plugins.Plugin;
import org.elasticsearch.xpack.core.security.authc.support.Hasher;
import org.elasticsearch.xpack.core.security.authc.support.UsernamePasswordToken;
import org.elasticsearch.xpack.security.LocalStateSecurity;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Rule;
import org.junit.rules.ExternalResource;
import java.nio.file.Path;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;
import java.util.stream.Collectors;
import static org.elasticsearch.test.SecuritySettingsSourceField.TEST_PASSWORD_SECURE_STRING;
import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
import static org.elasticsearch.xpack.core.security.authc.support.UsernamePasswordToken.basicAuthHeaderValue;
import static org.elasticsearch.xpack.security.support.SecuritySystemIndices.SECURITY_MAIN_ALIAS;
import static org.hamcrest.Matchers.hasItem;
/**
 * Base class to run tests against a cluster with X-Pack installed and security enabled.
 * The default {@link org.elasticsearch.test.ESIntegTestCase.Scope} is {@link org.elasticsearch.test.ESIntegTestCase.Scope#SUITE}
 *
 * @see SecuritySettingsSource
 */
public abstract class SecurityIntegTestCase extends ESIntegTestCase {