使用NSURLConnection进行单元测试 [英] Unit testing with NSURLConnection

问题描述

我想测试一段使用网络的代码(具体来说是NSURLConnection类).该代码(简称为NetworkManager)看起来像这样:

I want to test a piece of code that uses network (the NSURLConnection class, to be specific). The code (let’s call it NetworkManager) looks a bit like this:

- (id) buildConnection
{
    // some more code and then:
    return [NSURLConnection …];
}

- (void) startNetworkSync
{
    id connection = [self buildConnection];
    //…
}

在单元测试中，我想摆脱网络连接，即.用模拟替换NSURLConnection对象.我该怎么做?

In the unit test I would like to get rid of the networking, ie. replace the NSURLConnection object by a mock. How do I do this?

我尝试创建NetworkManager的部分模拟，该模拟将用存根替换buildConnection方法.问题是 OCMock 所做的部分模拟仅对来自外部世界的消息进行存根–从startNetworkSync发送buildConnection会调用原始方法，而不是存根.

I’ve tried creating a partial mock of the NetworkManager that would replace the buildConnection method by a stub. The problem is that partial mocks as done by OCMock only stub messages from the outside world – sending buildConnection from the startNetworkSync invokes the original method, not the stub.

我还尝试通过类别对NetworkManager类进行猴子修补.这行得通，我可以轻松地用其他代码覆盖buildConnection方法，并用存根替换真正的NSURLConnection.问题是我发现没有简单的方法可以在测试中获得存根连接-该连接是NetworkManager的私有部分.

I have also tried monkey-patching the NetworkManager class through a category. This works, I can easily override the buildConnection method by other code and replace the real NSURLConnection with a stub. The problem is that I found no simple way I could get the stubbed connection in the test – the connection is a private part of the NetworkManager.

然后，我可以将NetworkManager子类化，重写buildConnection方法，并为创建的连接添加实例变量和访问器.不过，这似乎是很多代码.

Then I could subclass the NetworkManager, override the buildConnection method and add an instance variable plus an accessor for the created connection. This seems like a lot of code, though.

您将如何解决?我正在寻找一种解决方案，以保持NetworkManager类的设计整洁，并且在测试中不需要太多魔术或代码.

How would you solve this? I am looking for a solution that keeps the NetworkManager class design clean and does not require much magic nor much code in the test.

推荐答案

这是依赖注入旨在解决的问题；如果使用startNetworkSyncWithConnection:(NSURLConnection*)，则可以通过模拟连接轻松测试该方法.如果您不想为客户更改API，则甚至可以保留startNetworkSync作为包装器，该包装器除了以[self buildConnection]作为参数调用该新方法外，什么也不做.

This is the kind of thing dependency injection is designed to solve; if you use startNetworkSyncWithConnection:(NSURLConnection*) instead you can easily test the method with a mock connection. If you don't want to change the API for your clients you could even keep startNetworkSync as a wrapper that does nothing but call that new method with [self buildConnection] as the argument.

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