Add IT with ping for java cluster client. (#893)

Add IT with ping for cluster client.

Signed-off-by: Yury-Fridlyand <[email protected]>

java/integTest/src/test/java/glide/cluster/CommandTests.java

@@ -1,6 +1,7 @@
 /** Copyright GLIDE-for-Redis Project Contributors - SPDX Identifier: Apache-2.0 */
 package glide.cluster;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import glide.TestConfiguration;
@@ -43,4 +44,11 @@ public void custom_command_info() {
             assertTrue(((String) info).contains("# Stats"));
         }
     }
+
+    @Test
+    @SneakyThrows
+    public void custom_command_ping() {
+        var data = clusterClient.customCommand(new String[] {"ping"}).get(10, TimeUnit.SECONDS);
+        assertEquals("PONG", data.getSingleValue());
+    }
 }