java - 使用mockito测试servlet的NullPointer异常

Question

我正在使用mockito来测试servlet

我的servlet的doGet方法是

@Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
                response.setContentType("application/json");
                PrintWriter out = response.getWriter();
                String servletPath = request.getServletPath();
                String servletInfo = request.getPathInfo();
                List<SchoolProperties> itemList = itemService.findAll();
                ItemParser itemParser = new ItemParser();
                itemParser.setJsonFactory(new JsonFactory());
                out.println(itemParser.parseItem(itemList));

        }

我的测试方法是

   @Test
    public void shouldPrintJsonString throws IOException, ServletException{
        HttpServletRequest req = mock(HttpServletRequest.class);
        HttpServletResponse res = mock(HttpServletResponse.class);
        ItemService is = mock(ItemService.class);
        ArrayList mockList = mock(ArrayList.class);

        SchoolProperties s1 = new SchoolProperties(1, "MyItemName", 5);
        SchoolProperties s2 = new SchoolProperties(1, "MyItemName", 5);
        mockList.add(s1);
        mockList.add(s2);



        StringWriter writer = new StringWriter();
        when(req.getServletPath()).thenReturn("/school_items");
        when(req.getMethod()).thenReturn("GET");
        when(req.getPathInfo()).thenReturn("/");
        when(is.findAll()).thenReturn(mockList);
        given(res.getWriter()).willReturn(new PrintWriter(writer));

        ItemController it = new ItemController();
        it.setItemService(is);

        it.service(req, res);
        String expectedResult="";
        verify(res).setContentType("application/json");
        verify(is.findAll(),atLeast(1));
        Assert.assertEquals(expectedResult, writer.toString());
        Assert.assertTrue(writer.toString().contains("["));
}

我在运行测试用例时遇到空指针异常。我怀疑我的 ItemParser 和 JsonFactory 没有在测试中创建或没有注入(inject)。它是否正确？如果是这样，如何在不更改 servlet 方法的情况下使其不为 null？

Answer 1

你的问题是你 mock 了 ArrayList ，这意味着它的 add方法不会执行任何操作，因此 s1和s2从未在列表中。不要 mock ArrayList - 使用真实的ArrayList相反。

还有verify(is.findAll(),atLeast(1));应该读 verify(is,atLeast(1)).findAll();