与多个合作者进行单元测试 [英] Unit testing with multiple collaborators

问题描述

今天我遇到了一个非常困难的TDD问题。我需要通过HTTP POST与服务器进行交互。我找到了Apache Commons HttpClient，它可以满足我的需求。

Today I ran into a very difficult TDD problem. I need to interact with a server through HTTP POSTs. I found the the Apache Commons HttpClient, which does what I need.

然而，我最终得到了来自Apache Commons的一堆协作对象：

However, I end up with a bunch of collaborating objects from Apache Commons:

public void postMessage(String url, String message) throws Exception {

    PostMethod post = new PostMethod(url);
    RequestEntity entity = new StringRequestEntity(message, 
                                      "text/xml; charset=ISO-8859-1");
    post.setRequestEntity(entity);
    HttpClient httpclient = new HttpClient();
    try {
        int result = httpclient.executeMethod(post);

        System.out.println("Response status code: " + result);
        System.out.println("Response body: ");
        System.out.println(post.getResponseBodyAsString());
    } finally {
        post.releaseConnection();
    }
}

我有 PostMethod object，一个 RequestEntity 对象和一个 HttpClient 对象。传递 HttpClient ala依赖注入感觉相对舒服，但我该如何处理其他协作者？

I have a PostMethod object, a RequestEntity object and a HttpClient object. I feel relatively comfortable passing in the HttpClient ala dependency injection, but what do I do about the other collaborators?

我可以创建一堆工厂方法（或工厂类）来创建协作者，但我有点害怕我会嘲笑太多。

I could create a bunch of factory methods (or a factory class) to create the collaborators, but I'm a bit afraid that I'd be mocking too much.

感谢您的回答！我剩下的问题是这样的方法：

Thanks for the answers! My remaining issue is a method like this:

public String postMessage(String url, String message) throws Exception {

    PostMethod post = new PostMethod(url);
    RequestEntity entity = new StringRequestEntity(message, 
                                      "text/xml; charset=ISO-8859-1");
    post.setRequestEntity(entity);
    HttpClient httpclient = new HttpClient();
    httpclient.executeMethod(post);
    return post.getResponseBodyAsString();
}

如何正确验证返回值是否来自 post.getResponseBodyAsString（）？我是否必须模拟发布以及客户？

How do I correctly verify that the returned value is from post.getResponseBodyAsString()? Would I have to mock post as well as client?

推荐答案

简答：模拟HttpClient，不要模拟PostMethod或RequestEntity。

Short answer: mock HttpClient, don't mock PostMethod or RequestEntity.

当然这是一个判断调用，但是我建议从嘲笑真正需要嘲笑的事情开始：HttpClient。 PostMethod和RequestEntity是堆栈本地的，快速的和确定的，我会保留它们，如果有必要，你可以随后嘲笑它们。正如您的代码现在一样，通过模拟PostMethod和RequestEntity，您会使api复杂化，使用api的代码变得复杂，并公开实现的详细信息。

随着代码的发展，您将拥有更好的代码想法需要嘲笑什么，现在不需要尝试预测未来。

Of course this is a judgement call, but I'd suggest start with mocking things that really need to be mocked: HttpClient. PostMethod and RequestEntity are stack-local, fast, and deterministic, I'd leave them as they are, you can always mock them later if necessary. As your code is now, by mocking PostMethod and RequestEntity you complicate your api, complicate the code that uses your api, and expose the details of your implementation.
As your code evolves, you'll have a better idea what needs to be mocked, no need to try to predict the future now.

这可能有用：

http://www.testingreflections.com/node/view/7417

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