CODEWITHSUNDEEP
javascriptunit-testingtestingjestjs
Ben
Ben

Reputation: 5414

Jest Mock - inserting values into tested file

I'm having trouble inserting values into the file under test:

import device from '../device'

let execute = () => {
  if (device.isAndroid()) {
    return true
  else {
    return false
  }
}

Now for the test file:

jest.mock('../device')
import device from '../device'

describe('when the device is Android', () => {
  let device

  beforeEach(() => {
    device = jest.fn().mockImplementation(() => {
      return { 
        isAndroid: () => { return true } 
      }
    })
  })

  it('returns true', () => {
    let results = execute()
    expect(result).toEqual(true)
  })
})

The test fails and returns false. What am I doing wrong?

Upvotes: 0

Views: 692

Answers (1)

Andreas Köberle
Andreas Köberle

Reputation: 110912

You need to mock '../device' with a jest spy and the mock implementation on that:

jest.mock('../device', ()=>{return {isAndroid: jest.fn()}})
import device from '../device'

describe('when the device is Android', () => {

  beforeEach(() => {
    device.isAndroid.mockImplementation(() => true)
  })

  it('returns true', () => {
    let results = execute()
    expect(result).toEqual(true)
  })
})

Upvotes: 1

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