move code to src/test

* so that it compiles and tests pass
* fix some additional snip references in getting started

akka-docs/src/test/java/jdocs/cluster/ClusterDocTest.java

@@ -0,0 +1,42 @@
+/**
+ * Copyright (C) 2015-2017 Lightbend Inc. <http://www.lightbend.com>
+ */
+package jdocs.cluster;
+
+import akka.testkit.javadsl.TestKit;
+import com.typesafe.config.ConfigFactory;
+import jdocs.AbstractJavaTest;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import akka.actor.ActorSystem;
+import akka.cluster.Cluster;
+
+
+public class ClusterDocTest extends AbstractJavaTest {
+  
+  static ActorSystem system;
+  
+  @BeforeClass
+  public static void setup() {
+    system = ActorSystem.create("ClusterDocTest", 
+        ConfigFactory.parseString(scala.docs.cluster.ClusterDocSpec.config()));
+  }
+
+  @AfterClass
+  public static void tearDown() {
+    TestKit.shutdownActorSystem(system);
+    system = null;
+  }
+
+  @Test
+  public void demonstrateLeave() {
+    //#leave
+    final Cluster cluster = Cluster.get(system);
+    cluster.leave(cluster.selfAddress());
+    //#leave
+
+  }
+
+}