cook-book.md

Tests cook book

Date

We use TZ=UTC environment variable so every serialized date are in UTC to prevent environment conflict.

You can mock the result of new Date() as follows:

const Today = new Date(2020, 10, 1)

describe('Favorites reducer', () => {
  beforeAll(() => {
    mockdate.set(Today)
  })
})

Authentication with authContext

When a component uses AuthContext, you first need to mock it at the top of the file:

import { useAuthContext } from 'features/auth/context/AuthContext'

jest.mock('features/auth/context/AuthContext')

Then you can use 2 different utils depending on your need.

If you want a disconnected user:

mockAuthContextWithoutUser()

If you want a logged in specific user:

mockAuthContextWithUser(anUserFixture)

If you want to persist your mock (using mockReturnValue instead of mockReturnValueOnce) you can pass the persist option as follows:

mockAuthContextWithoutUser({ persist: true })
mockAuthContextWithUser(anUserFixture, { persist: true })

Mock route params

When the tested component use route params through useRoute hook, params can be mocked as follows:

import { useRoute } from '__mocks__/@react-navigation/native'

// later
useRoute.mockReturnValue({
  params: {
    shouldDisplayLoginModal: withModal,
  },
})

Test that the user sees a snackbar

1. Mock the snackbar context at the beginning of the file

const mockShowErrorSnackBar = jest.fn()
const mockShowInfoSnackBar = jest.fn()
jest.mock('ui/components/snackBar/SnackBarContext', () => ({
  useSnackBarContext: () => ({
    showErrorSnackBar: mockShowErrorSnackBar,
    showInfoSnackBar: mockShowInfoSnackBar,
  }),
}))

2. In your test, assert that the mock has been called with the message that is supposed to be displayed in the snackBar, and with the correct timeout.

expect(mockShowErrorSnackBar).toHaveBeenCalledWith({
  message:
    'Ton compte Google semble ne pas être valide. Pour pouvoir te connecter, confirme d’abord ton adresse e-mail Google.',
  timeout: SNACK_BAR_TIME_OUT_LONG,
})