Go 中的模拟函数 [英] Mock functions in Go

问题描述

我对依赖感到困惑.我希望能够用模拟函数调用替换一些函数调用.这是我的代码片段:

I'm puzzled with dependencies. I want to be able to replace some function calls with mock ones. Here's a snippet of my code:

func get_page(url string) string {
    get_dl_slot(url)
    defer free_dl_slot(url)
    
    resp, err := http.Get(url)
    if err != nil { return "" }
    defer resp.Body.Close()
    
    contents, err := ioutil.ReadAll(resp.Body)
    if err != nil { return "" }
    return string(contents)
}

func downloader() {
    dl_slots = make(chan bool, DL_SLOT_AMOUNT) // Init the download slot semaphore
    content := get_page(BASE_URL)
    links_regexp := regexp.MustCompile(LIST_LINK_REGEXP)
    matches := links_regexp.FindAllStringSubmatch(content, -1)
    for _, match := range matches{
        go serie_dl(match[1], match[2])
    }
}

我希望能够在不实际通过 http 获取页面的情况下测试 downloader() - 即通过模拟 get_page(更容易，因为它只返回页面内容作为字符串)或 http.Get().

I'd like to be able to test downloader() without actually getting a page through http - i.e. by mocking either get_page (easier since it returns just the page content as a string) or http.Get().

我发现了这个话题，这似乎是关于类似的问题.Julian Phillips 提出了他的库 Withmock 作为解决方案，但我无法让它工作.这是我的测试代码的相关部分，老实说，这些代码对我来说主要是货物崇拜代码:

I found this thread which seems to be about a similar problem. Julian Phillips presents his library, Withmock as a solution, but I'm unable to get it to work. Here's the relevant parts of my testing code, which is largely cargo cult code to me, to be honest:

import (
    "testing"
    "net/http" // mock
    "code.google.com/p/gomock"
)
...
func TestDownloader (t *testing.T) {
    ctrl := gomock.NewController()
    defer ctrl.Finish()
    http.MOCK().SetController(ctrl)
    http.EXPECT().Get(BASE_URL)
    downloader()
    // The rest to be written
}

测试输出如下:

错误:无法安装_et/http":退出状态 1 输出:无法加载包:包 _et/http:找到包 http (chunked.go) 和 main(main_mock.go) 在
/var/folders/z9/ql_yn5h550s6shtb9c5sggj40000gn/T/withmock570825607/path/src/_et/http

ERROR: Failed to install '_et/http': exit status 1 output: can't load package: package _et/http: found packages http (chunked.go) and main (main_mock.go) in
/var/folders/z9/ql_yn5h550s6shtb9c5sggj40000gn/T/withmock570825607/path/src/_et/http

Withmock 是我测试问题的解决方案吗?我应该怎么做才能让它工作?

Is the Withmock a solution to my testing problem? What should I do to get it to work?

推荐答案

就我个人而言，我不使用 gomock(或任何与此相关的模拟框架；没有它，在 Go 中模拟非常容易).我要么将依赖项作为参数传递给 downloader() 函数，要么让 downloader() 成为一个类型的方法，并且该类型可以保存 downloader()code>get_page 依赖:

Personally, I don't use gomock (or any mocking framework for that matter; mocking in Go is very easy without it). I would either pass a dependency to the downloader() function as a parameter, or I would make downloader() a method on a type, and the type can hold the get_page dependency:

type PageGetter func(url string) string

func downloader(pageGetterFunc PageGetter) {
    // ...
    content := pageGetterFunc(BASE_URL)
    // ...
}

主要内容:

func get_page(url string) string { /* ... */ }

func main() {
    downloader(get_page)
}

测试:

func mock_get_page(url string) string {
    // mock your 'get_page()' function here
}

func TestDownloader(t *testing.T) {
    downloader(mock_get_page)
}

方法2:使download()成为Downloader类型的方法:

如果您不想将依赖项作为参数传递，您还可以将 get_page() 设为类型的成员，并将 download() 设为该类型的方法，然后可以使用 get_page:

Method2: Make download() a method of a type Downloader:

If you don't want to pass the dependency as a parameter, you could also make get_page() a member of a type, and make download() a method of that type, which can then use get_page:

type PageGetter func(url string) string

type Downloader struct {
    get_page PageGetter
}

func NewDownloader(pg PageGetter) *Downloader {
    return &Downloader{get_page: pg}
}

func (d *Downloader) download() {
    //...
    content := d.get_page(BASE_URL)
    //...
}

主要内容:

func get_page(url string) string { /* ... */ }

func main() {
    d := NewDownloader(get_page)
    d.download()
}

测试:

func mock_get_page(url string) string {
    // mock your 'get_page()' function here
}

func TestDownloader() {
    d := NewDownloader(mock_get_page)
    d.download()
}

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