throw a JedisConnectionException if unsubscribing from a not subscribed JedisPubSub instance

src/main/java/redis/clients/jedis/JedisPubSub.java

@@ -10,6 +10,7 @@ import static redis.clients.jedis.Protocol.Keyword.UNSUBSCRIBE;
 import java.util.Arrays;
 import java.util.List;
 
+import redis.clients.jedis.exceptions.JedisConnectionException;
 import redis.clients.jedis.exceptions.JedisException;
 import redis.clients.util.SafeEncoder;
 
@@ -31,6 +32,10 @@ public abstract class JedisPubSub {
     public abstract void onPSubscribe(String pattern, int subscribedChannels);
 
     public void unsubscribe() {
+        if (client == null) {
+            throw new JedisConnectionException(
+                    "JedisPubSub was not subscribed to a Jedis instance.");
+        }
         client.unsubscribe();
         client.flush();
     }

src/test/java/redis/clients/jedis/tests/commands/PublishSubscribeCommandsTest.java

@@ -9,6 +9,7 @@ import org.junit.Test;
 import redis.clients.jedis.BinaryJedisPubSub;
 import redis.clients.jedis.Jedis;
 import redis.clients.jedis.JedisPubSub;
+import redis.clients.jedis.exceptions.JedisConnectionException;
 import redis.clients.jedis.exceptions.JedisDataException;
 import redis.clients.util.SafeEncoder;
 
@@ -501,4 +502,29 @@ public class PublishSubscribeCommandsTest extends JedisCommandTestBase {
             // this is OK because we are not sending AUTH command
         }
     }
+
+    @Test(expected = JedisConnectionException.class)
+    public void unsubscribeWhenNotSusbscribed() throws InterruptedException {
+        JedisPubSub pubsub = new JedisPubSub() {
+            public void onMessage(String channel, String message) {
+            }
+
+            public void onPMessage(String pattern, String channel,
+                    String message) {
+            }
+
+            public void onSubscribe(String channel, int subscribedChannels) {
+            }
+
+            public void onUnsubscribe(String channel, int subscribedChannels) {
+            }
+
+            public void onPUnsubscribe(String pattern, int subscribedChannels) {
+            }
+
+            public void onPSubscribe(String pattern, int subscribedChannels) {
+            }
+        };
+        pubsub.unsubscribe();
+    }
 }