Add test to ensure that ShieldServerTransportService wraps all handlers

This commit adds a test to ensure that all request handlers are wrapped
by ProfileSecuredRequestHandler.

Original commit: elastic/x-pack-elasticsearch@26473d0ddc

shield/src/main/java/org/elasticsearch/shield/transport/ShieldServerTransportService.java

@@ -111,7 +111,7 @@ public class ShieldServerTransportService extends TransportService {
         return profileFilters.get(profile);
     }
 
-    static class ProfileSecuredRequestHandler<T extends TransportRequest> implements TransportRequestHandler<T> {
+    public static class ProfileSecuredRequestHandler<T extends TransportRequest> implements TransportRequestHandler<T> {
 
         protected final String action;
         protected final TransportRequestHandler<T> handler;

shield/src/test/java/org/elasticsearch/transport/ShieldServerTransportServiceTests.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.transport;
+
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.shield.ShieldPlugin;
+import org.elasticsearch.shield.transport.ShieldServerTransportService;
+import org.elasticsearch.test.ShieldIntegTestCase;
+
+import java.util.Map;
+
+import static org.hamcrest.Matchers.instanceOf;
+
+// this class sits in org.elasticsearch.transport so that TransportService.requestHandlers is visible
+public class ShieldServerTransportServiceTests extends ShieldIntegTestCase {
+    @Override
+    protected Settings transportClientSettings() {
+        return Settings.settingsBuilder()
+                .put(super.transportClientSettings())
+                .put(ShieldPlugin.ENABLED_SETTING_NAME, true)
+                .build();
+    }
+
+    public void testShieldServerTransportServiceWrapsAllHandlers() {
+        for (TransportService transportService : internalTestCluster().getInstances(TransportService.class)) {
+            assertThat(transportService, instanceOf(ShieldServerTransportService.class));
+            for (Map.Entry<String, RequestHandlerRegistry> entry : transportService.requestHandlers.entrySet()) {
+                assertThat(
+                        "handler not wrapped by " + ShieldServerTransportService.ProfileSecuredRequestHandler.class + "; do all the handler registration methods have overrides?",
+                        entry.getValue().getHandler(),
+                        instanceOf(ShieldServerTransportService.ProfileSecuredRequestHandler.class)
+                );
+            }
+        }
+    }
+}