Stubbing methods in Golang unit testing

Question

I've been thinking about this whole night, but still cannot find an elegant way to do this thing. Let's say I have a struct

type file struct {
    x int
}

func (f *file) filename() string {
    return fmt.Sprintf("%s/%d.log", exportPath, f.x)
}

func (f *file) write(data []byte) {
    ...
    aFile = os.File.Open(f.filename())
    ...
}

Now I want to test write method and stub filename method to return temp filename. How can I do this? To the moment I found two options:

declare filename = func(f* file) and override it in test
make filename a field of the struct

But they both seem wrong in this case. So the question is - can I stub in any way this method? And in general - how to stub internal methods for testing (for external obviously dependency injection could work)

SunRunAway · Accepted Answer · 2016-01-20 18:07:14Z

2

Making filename a field of the struct is an elegant way. The filename should be defined when new the struct.

type fileStruct {
    filename string
}

func newFileStruct(x int) *fileStruct {
    filename := fmt.Sprintf("%s/%d.log", exportPath, x)
    return &fileStruct{filename: filename}
}

func (f *fileStruct) write (data []byte) {
    ...
    file = os.File.Open(f.filename)
    ...
}

answered Jan 20, 2016 at 18:07

SunRunAway

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Comments

AlexeyKarasev · Accepted Answer · 2016-01-20 19:23:59Z

1

Ended up making my structs 100% injectable, the code looks clear and concise and tests like a charm!

answered Jan 20, 2016 at 19:23

AlexeyKarasev

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