测试接受未在Golang中返回值的回调函数的方法

Question

我正在尝试测试以下函数：

// SendRequestAsync sends request asynchronously, accepts callback
//  func, which it invokes
//
// Parameters:
// - `context` : some context
// - `token` : some token
// - `apiURL` : the URL to hit
// - `callType` : the type of request to make. This should be one of
//  the HTTP verbs (`"GET"`, `"POST"`, `"PUT"`, `"DELETE"`, ...)
// - `callBack` : the func to invoke upon completion
// - `callBackCustomData`: the data to invoke `callBack` with
//
// Since this is an async request, it doesn't return anything.
func (a *APICoreSt) SendRequestAsync(context interface{}, token string, apiURL string, callType APIType, header map[string]string, jsonBody []byte,
    callBack OnCompletion, callBackCustomData interface{}) {
    go func(data interface{}) {
        callBack(a.SendRequest(context, token, apiURL, callType, header, jsonBody), data)
    }(callBackCustomData)
}

其中，OnCompletion由以下各项定义：

type OnCompletion func(result CallResultSt, data interface{})

我的大脑立即想到创建一个间谍回调。为此，我对this framework进行了派生，得出了以下结果：

// outside the test function
type MySpy struct {
    *spies.Spy
}

func (my *MySpy) Callback(res CallResultSt, data interface{}) {
    my.Called(res, data)
    fmt.Println("Hello world")
    return
}

//in the test function
spy := new(MySpy)

//...some table-driven test logic the generator came up with, containing my data

spy.MatchMethod("Callback", spies.AnyArgs)
assert.NotEmpty(t, spies.CallsTo("Callback"))

它对我的问候是

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
    panic: runtime error: invalid memory address or nil pointer dereference

我如何纠正这个问题，并测试这个方法呢？

Answer 1

我会抛弃间谍的东西。这项任务非常简单，您不应该需要外部依赖来处理它。相反，您可以创建自己的"spy“，它在调用函数时将args传递到一个通道中。在您的测试中，然后尝试从通道接收。这将强制测试等待回调函数被调用。您还可以考虑添加超时期限，以便测试可以失败，而不是在从未调用函数的情况下永远阻塞。

// outside the test function
type MySpy struct {
    Args chan MySpyArgs
}

type MySpyArgs struct {
    Res  CallResultSt
    Data interface{}            
}

func (my *MySpy) Callback(res CallResultSt, data interface{}) {
    my.Args <- MySpyArgs{Res: res, Data: data}
}

//in the test function
spyChan := make(chan MySpyArgs)
spy := &MySpy{spyChan}

//...some table-driven test logic the generator came up with, containing my data

args := <-spyChan
// can now assert arguments were as you expected, etc.

一个简单的工作示例：https://play.golang.org/p/zUYpjXdkz-4。

如果你想使用超时：

...
select {
case args := <-spyChan:
    // assertions on args
case <-time.After(5 * time.Second):
    // prevent blocking for over 5 seconds and probably fail the test
}