问如何模拟Google App Engine服务的答案(例如blobstore)

EN

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    Gson gson = new Gson();
    Map<String, String> result = new HashMap<String, String>();
    result.put("uploadurl", BlobstoreServiceFactory.getBlobstoreService()
            .createUploadUrl("/api/v1/import"));
    gson.toJson(result, resp.getWriter());
}

public class ImportServletTest {
   public static class Response {
    String uploadurl;

    void setUploadurl(String url) {
        this.uploadurl = url;
    }
}

private LocalBlobstoreServiceTestConfig blobstoreConfig = new LocalBlobstoreServiceTestConfig();

private LocalServiceTestHelper helper = new LocalServiceTestHelper(blobstoreConfig);
@Test
public void getsUploadURL() throws IOException, ServletException {
    ImportServlet servlet = new ImportServlet();

    HttpServletResponse response = mock(HttpServletResponse.class);
    try (CharArrayWriter output = new CharArrayWriter();
            PrintWriter writer = new PrintWriter(output);) {
        when(response.getWriter()).thenReturn(writer);

        servlet.doGet(null, response);
        writer.flush();

        Response apiResponse = new Gson().fromJson(output.toString(), Response.class);
        assertEquals("http://mysite/_ah/theurl", apiResponse.uploadurl);
    }
}

@Before
public void setupGae() throws IOException {
    helper.setUp();
}

@After
public void teardownGae() {
    helper.tearDown();
}
}