如何在golang中模拟request.Request

Question

I'm using github.com/aws/aws-sdk-go/aws/request to get presigned URLs, which I need to upload files to s3 bucket in AWS. I'm writing the test currently, for that I need to mock func (r *Request) Presign(expire time.Duration). request.Request is a struct, not an interface, so i have no idea, how can I mock it.

Answer 1

This isn't directly answering your question, but it might remove the basis of the question altogether.

A neat thing in Go, is that you are able to easily isolate your dependencies using interfaces. If your code, the part that you need to test, is using Presign indirectly, it is trivial to test.

I.e. create an interface

type HigherLevelAws interface {
    Upload(file string) error
}

and use this interface in your code, along with Upload. Then you can easily mock this using e.g. https://godoc.org/github.com/stretchr/testify/mock

The actual implementation, would look something like this

type ActualAwsImpl struct {
    aws *aws.Client
}

func (a *ActualAwsImpl) Upload(file string) error {
    aws.Presign...
}

This allows you to test the business part of your code, but of course, still leaves untested code in ActualAwsImpl. This untested code, however, may be guaranteed to work by virtue of unit and integration tests in the aws sdk itself. Either way, in my organization, we test this using fake aws services run in docker (e.g. https://github.com/gliffy/fake-s3).