### Question:
AbstractContact implements IContact { public void setLastMessage(IMessage lastMessage) { this.lastMessage = lastMessage; }  boolean isUnknown(); void setUnknown(boolean unknown); boolean isNewbie(); void setNewbie(boolean newbie); IMessage getLastMessage(); void setLastMessage(IMessage lastMessage); int getUnread(); void setUnread(int unread); void clearUnRead(); void increaceUnRead(); int compareTo(AbstractContact that);  }### Answer:
@Test public void testSetLastMessage() { MockMessage m = new MockMessage("m1"); contact.setLastMessage(m); MockMessage m2 = new MockMessage("m2"); contact.setLastMessage(m2); assertEquals(m2, contact.getLastMessage()); }