@Test
public void testGetHeaders() {

  final SimpleMessage message = new SimpleMessage();
  assertNotNull(message.getHeaders());
  assertTrue(message.getHeaders().isEmpty());
  final String senderName = "test";
  message.addHeader(Message.Headers.SENDER, senderName);
  assertNotNull(message.getHeaders());
  assertFalse(message.getHeaders().isEmpty());
  assertEquals(senderName, message.getHeaders().get(Message.Headers.SENDER));
}