### Question:
PushMessage { public String getMessageId() { return messageId; } PushMessage(String recipient, String body, String subject, String messageId);  PushMessage(String recipient, String body, String subject); String getRecipient(); String getBody(); String getSubject(); String getMessageId(); static final String MESSAGE_ID; }### Answer:
@Test public void checkMessageIdIsFilled() { PushMessage pm = new PushMessage("recipient", "message", "subject"); assertThat(pm.getMessageId()).isNotNull(); }