### Question:
MessageStreamScriptService implements ScriptService { public boolean postDirectMessageToUser(String message, DocumentReference user) { try { this.stream.postDirectMessageToUser(message, user); return true; } catch (Exception e) { setError(e); return false; } }  boolean postPublicMessage(String message); boolean postPersonalMessage(String message); boolean postDirectMessageToUser(String message, DocumentReference user); boolean postMessageToGroup(String message, DocumentReference group); boolean deleteMessage(String id); boolean isActive(); Exception getLastError();  }### Answer:
@Test public void postDirectMessage() throws Exception { assertTrue(this.streamService.postDirectMessageToUser("Hello World!", this.targetUser)); MessageStream stream = this.mocker.getInstance(MessageStream.class); verify(stream).postDirectMessageToUser("Hello World!", this.targetUser); }