diff --git a/elasticsearch/x-pack/security/src/test/java/org/elasticsearch/xpack/security/SecurityTests.java b/elasticsearch/x-pack/security/src/test/java/org/elasticsearch/xpack/security/SecurityTests.java
index a04880ebb12..784f9e214b9 100644
--- a/elasticsearch/x-pack/security/src/test/java/org/elasticsearch/xpack/security/SecurityTests.java
+++ b/elasticsearch/x-pack/security/src/test/java/org/elasticsearch/xpack/security/SecurityTests.java
@@ -5,29 +5,71 @@
  */
 package org.elasticsearch.xpack.security;
 
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.test.ESTestCase;
-import org.junit.Before;
+import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.xpack.extensions.XPackExtension;
+import org.elasticsearch.xpack.security.authc.Realm;
+import org.elasticsearch.xpack.security.authc.Realms;
+import org.elasticsearch.xpack.security.authc.file.FileRealm;
+
+import static org.mockito.Mockito.mock;
 
 public class SecurityTests extends ESTestCase {
 
-    private Environment env;
+    public static class DummyExtension extends XPackExtension {
+        private String realmType;
+        DummyExtension(String realmType) {
+            this.realmType = realmType;
+        }
+        @Override
+        public String name() {
+            return "dummy";
+        }
+        @Override
+        public String description() {
+            return "dummy";
+        }
+        @Override
+        public Map<String, Realm.Factory> getRealms() {
+            return Collections.singletonMap(realmType, config -> null);
+        }
+    }
 
-    @Before
-    public void setupEnv() {
-        Settings settings = Settings.builder()
+    private Collection<Object> createComponents(Settings testSettings, XPackExtension... extensions) throws IOException {
+        Settings settings = Settings.builder().put(testSettings)
             .put("path.home", createTempDir()).build();
-        env = new Environment(settings);
+        Environment env = new Environment(settings);
+        Security security = new Security(settings, env);
+        ThreadPool threadPool = mock(ThreadPool.class);
+        return security.createComponents(null, threadPool, null, Arrays.asList(extensions));
+    }
+
+    private <T> T findComponent(Class<T> type, Collection<Object> components) {
+        for (Object obj : components) {
+            if (type.isInstance(obj)) {
+                return type.cast(obj);
+            }
+        }
+        throw new AssertionError("Could not find component of type " + type + " in components");
     }
 
     public void testCustomRealmExtension() throws Exception {
-        Security security = new Security(Settings.EMPTY, env);
-
-        //security.createComponents(null, null, null, )
+        Collection<Object> components = createComponents(Settings.EMPTY, new DummyExtension("myrealm"));
+        Realms realms = findComponent(Realms.class, components);
+        assertNotNull(realms.realmFactory("myrealm"));
     }
 
     public void testCustomRealmExtensionConflict() throws Exception {
-
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class,
+            () -> createComponents(Settings.EMPTY, new DummyExtension(FileRealm.TYPE)));
+        assertEquals("Realm type [" + FileRealm.TYPE + "] is already registered", e.getMessage());
     }
 }