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How might we utilize snapshots for arguments matching? #17

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Whoaa512 opened this Issue Apr 5, 2019 · 1 comment

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Whoaa512 commented Apr 5, 2019

I have a use case where I'm generating a relatively large payload and I'd like when to make a snapshot for one of the arguments.

Example code

import { when } from 'jest-when'

const fn = jest.fn()

test('match snap', () => {
    expect.hasAssertions()

    when(fn)
        .expectCalledWith(expect.toMatchSnapshot())
        .mockReturnValueOnce('hi')

    expect(fn({ bar: { a: 12 } })).toEqual('hi')
})

Basically I want to jest-when to look at the arg and if I pass the asymmetric snapshot matcher to use expect(arg).toMatchSnapshot() instead of the normal .toEqual

What do you think?

For context, expect.toMatchSnapshot() is only available in jest 23+, and even then expect.toMatchSnapshot() doesn't actually work like you'd expect.

@timkindberg

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timkindberg commented Apr 5, 2019

I don't think you can use toMatchSnapshot in that fashion... it has to be used as an assertion only. I think you'd have to import the payload then assert it equals the snapshot then pass it to expectCalledWith.

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