Gmail Api Java Client - Use mockito/powermock example to mock Gmail API calls

Question

We are using the Gmail API Java Client version 1.19.0. Is there anyone that has implemented successfully a working mock object that could be used for stubing requests such as:

gmailClient.users().history().list("me").setStartHistoryId(startHistoryId).setPageToken(pageToken).execute();

Essentially, we would like to stub the above call and create a specific response, to test different business scenarios.

Answer 1

Please check below a working example of the above question. No need to use powermock. Mockito is only needed.

    @Before
    public void init() throws Exception{
        ListHistoryResponse historyResponse = new ListHistoryResponse();
        historyResponse.setHistoryId(BigInteger.valueOf(1234L));
        List<History> historyList = new ArrayList<>();
        History historyEntry = new History();
        Message message = new Message();
        message.setId("123456");
        message.setThreadId("123456");
        List<Message> messages = new ArrayList<>();
        messages.add(message);
        historyEntry.setMessages(messages);
        historyList.add(historyEntry);

        mock = mock(Gmail.class);
        Gmail.Users users = mock(Gmail.Users.class);
        Gmail.Users.History history = mock(Gmail.Users.History.class);
        Gmail.Users.History.List list = mock(Gmail.Users.History.List.class);
        when(mock.users()).thenReturn(users);
        when(users.history()).thenReturn(history);
        when(history.list("me")).thenReturn(list);
        when(list.setStartHistoryId(BigInteger.valueOf(123L))).thenReturn(list);
        when(list.setPageToken(null)).thenReturn(list);
        when(list.execute()).thenReturn(historyResponse);

}