java - 如何模拟 servletContext 而不是 Servlet 或 HttpServletRequest？

Question

我有一个编写测试用例的独立项目；问题是我不能模拟 HttpServletRequest，因为在我的 servlet 中有像 getServletContext() 这样的调用，因为测试用例是从外部 servlet 容器运行的。它总是会返回一个错误，说“找不到上下文”。这只是 servlet 容器的一个依赖项；可以有数百个。例如，initialContext.lookup() 也依赖于一个容器。

这种场景下如何使用Mockito编写测试用例？请不要询问错误信息；这与其说是技术问题，不如说是逻辑问题。

在互联网上寻找教程让我想知道我是否做错了什么。之前似乎没有人遇到过这个问题......你怎么能模拟 HttpServletRequest 而没有在 servlet 中调用 getServletContext() ？我是说真的，它能有多罕见？

Answer 1

您有一个使用 ServletContext 的 servlet 实现，例如

public class SomeServlet extends HttpServlet{

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = getServletContext();
        Object attribute = servletContext.getAttribute("test");
        System.out.println(attribute.toString());
   }
}

在这种情况下，您有 2 个选项来测试 doGet 方法

使用 powermock 的 partitial mocking仅模拟 getServletContext 方法。

@RunWith(PowerMockRunner.class)
public class SomeServletTest {

    @Test
    public void onGet() throws ServletException, IOException{
        SomeServlet someServlet = PowerMock.createPartialMock(SomeServlet.class, "getServletContext");   
        ServletContext servletContext = PowerMock.createNiceMock(ServletContext.class);
        HttpServletRequest httpServletRequest = PowerMock.createNiceMock(HttpServletRequest.class);
        HttpServletResponse httpServletResponse = PowerMock.createNiceMock(HttpServletResponse.class);

        someServlet.getServletContext();
        PowerMock.expectLastCall().andReturn(servletContext);

        servletContext.getAttribute("test");
        PowerMock.expectLastCall().andReturn("hello");

        PowerMock.replay(someServlet, servletContext, httpServletRequest, httpServletResponse);

        someServlet.doGet(httpServletRequest, httpServletResponse);
    }
}

或者更简单的方法是覆盖 getServletContext 方法。在这种情况下，您不需要 powermock。您可以使用 easymock 来完成。例如

public class SomeServletTest {

    @Test
    public void onGet() throws ServletException, IOException{
        HttpServletRequest httpServletRequest = EasyMock.createNiceMock(HttpServletRequest.class);
        HttpServletResponse httpServletResponse = EasyMock.createNiceMock(HttpServletResponse.class);
        final ServletContext servletContext = EasyMock.createNiceMock(ServletContext.class);
        SomeServlet someServlet = new SomeServlet(){
            public ServletContext getServletContext() {
                return servletContext; // return the mock
            }
        };

        EasyMock.expect(servletContext.getAttribute("test")).andReturn("hello");
        EasyMock.replay(servletContext, httpServletRequest, httpServletResponse);

        someServlet.doGet(httpServletRequest, httpServletResponse);
    }
}

there can be 100's. like initialContext.lookup() also dependent on container.

在这种情况下，您可以创建一个 InitialContext 模拟并使用它。如果您的代码创建了一个新的 InitialContext，例如

public void someMethod(){
    InitialContext context = new InitialContext();
    context.lookup(....);
}

您可以简单地将 InitialContext 实例提取到一个 protected 方法中，您可以在您的测试中覆盖该方法，就像我上面使用 ServletContext

展示的那样

public void someMethod(){
    InitialContext context = createInitialContext();
    context.lookup(....);
}

protected InitialContext createInitialContext(){
    return new InitialContext(); // can be overridden by a subclass 
                                 // and therefore by tests as well to
                                 // return a mock
}

如果你不想或者不能这样修改代码，那么你可以使用Powermock来intercept the constructor .

编辑

Can you post your Mockito code? It would be a pleasure, since the methods are named differently.

@Test
public void onGet() throws ServletException, IOException {
  HttpServletRequest httpServletRequest = Mockito.mock(HttpServletRequest.class);
  HttpServletResponse httpServletResponse = Mockito.mock(HttpServletResponse.class);
  final ServletContext servletContext = Mockito.mock(ServletContext.class);
  SomeServlet someServlet = new SomeServlet(){
    public ServletContext getServletContext() {
      return servletContext; // return the mock
    }
  };

  Mockito.doReturn("hello").when(servletContext).getAttribute("test");

  someServlet.doGet(httpServletRequest, httpServletResponse);
}