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How to mock with a callback? #7

Whoaa512 opened this Issue Nov 6, 2018 · 1 comment


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Whoaa512 commented Nov 6, 2018

I've got a mock which needs to call a callback. Currently this is not possible with your library.

As a workaround I've got this:

myMock.mockImplementationOnce((...args) => {
            Bucket: 'attachments',
            Key: 'some-guid',
            Expires: 900,
            ContentType: 'application/pdf',

    const cb = _.last(args)

    cb(null, 'https://signed-url')

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timkindberg commented Nov 7, 2018

Ok so that behavior of calling a callback in jest is only possible via mockImplementation, since there is no convenient yield method like sinon.js has. So we essentially need to add mockImplementation to jest-when.

We could add new methods that worked like this:


A PR for these additions would be appreciated.

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