### Question:
TransactionalMessageBridge { public MessageExt lookMessageByOffset(final long commitLogOffset) { return this.store.lookMessageByOffset(commitLogOffset); } TransactionalMessageBridge(BrokerController brokerController, MessageStore store); long fetchConsumeOffset(MessageQueue mq); Set<MessageQueue> fetchMessageQueues(String topic); void updateConsumeOffset(MessageQueue mq, long offset); PullResult getHalfMessage(int queueId, long offset, int nums); PullResult getOpMessage(int queueId, long offset, int nums); PutMessageResult putHalfMessage(MessageExtBrokerInner messageInner); boolean putOpMessage(MessageExt messageExt, String opType); PutMessageResult putMessageReturnResult(MessageExtBrokerInner messageInner); boolean putMessage(MessageExtBrokerInner messageInner); MessageExtBrokerInner renewImmunityHalfMessageInner(MessageExt msgExt); MessageExtBrokerInner renewHalfMessageInner(MessageExt msgExt); MessageExt lookMessageByOffset(final long commitLogOffset); BrokerController getBrokerController();  }### Answer:
@Test public void testLookMessageByOffset(){ when(messageStore.lookMessageByOffset(anyLong())).thenReturn(new MessageExt()); MessageExt messageExt = transactionBridge.lookMessageByOffset(123); assertThat(messageExt).isNotNull(); }