go - 如何使用 Go 接口(interface)来测试 Google API Golang 库？

Question

我正在尝试使用接口(interface)来测试使用 google's drive api lib 的代码.

type MyFile struct {
  DownloadUrl string `json:"downloadUrl,omitempty"`
}

type MyFilesGetCall interface {
  Do() (*MyFile, error)
  // Do() (*drive.File, error) // this DOES work
}

type MyFilesService interface {
  Get(string) *MyFilesGetCall
  // Get(string) *drive.FilesGetCall // this DOES work
}

func GetInfo(id string, myService MyFilesService) {
  myService.Get(id).Do()
}

func main() {
  drive, _ := drive.New(new(http.Client))
  GetInfo("id", drive.Files)
}

当我尝试运行它时，出现以下错误:

$ go run so.go
./so.go:24: cannot use drive.Files (type *drive.FilesService) as type MyFilesService in argument to GetInfo:
        *drive.FilesService does not implement MyFilesService (wrong type for Get method)
                have Get(string) *drive.FilesGetCall
                want Get(string) *MyFilesGetCall
./so.go:28: fService.Get(id).Do undefined (type *MyFilesGetCall has no field or method Do)

接口(interface)似乎只能在 1 层深度工作。

谁能推荐一种替代方法来模拟这种依赖性？

Answer 1

It seems that interfaces only work 1 level deep.

Go 没有协变/协变的概念。 Get 的签名与 MyFilesService 接口(interface)不兼容。正如您的错误消息告诉您的那样:

*drive.FilesService does not implement MyFilesService (wrong type for Get method)
    have Get(string) *drive.FilesGetCall
    want Get(string) *MyFilesGetCall

Can anyone recommend an alternative approach for mocking this dependency?

将 MyFilesService 更改为 *drive.FilesService 实际实现的内容。