@Test
 public void testEmptyMessage() {
   JsonObject message = writer.createMessage();
   JsonObject head = message.get("head").asObject();
   assertEquals(0, head.size());
   JsonArray operations = message.get("operations").asArray();
   assertEquals(0, operations.size());
 }
  @Test
  public void testAppendMixedArrayParameter() {
    writer.appendSet(shellId, "key", new JsonArray().add(23).add("Hello"));

    SetOperation operation = (SetOperation) getMessage().getOperation(0);
    JsonArray property = operation.getProperty("key").asArray();
    assertEquals(2, property.size());
    assertEquals(23, property.get(0).asInt());
    assertEquals("Hello", property.get(1).asString());
  }