CODEWITHSUNDEEP
javascriptreactjsjestjs
user11092881
user11092881

Reputation:

Jest mock for dates doesn't work at all and returns its constructor

beforeAll(() => {
    ...
    const mockedData = '2020-11-26T00:00:00.000Z'

    jest.spyOn(global, 'Date').mockImplementation(() => mockedData)

    Date.now = () => 1606348800
})

describe('getIventory', () => {
    it('should make the appropriate fetch call', async () => {
        await inventoryStore.getInventory()
        expect(db.listInv).toHaveBeenCalledWith(query)
    })
})

I get:

 Object {
    "expected": Object {
-     "$lte": "2020-11-26T00:00:00.000Z",
+     "$lte": mockConstructor {},
    }
  },

This is my query object:

const query = {
    expected: { $lte: '2020-11-26T00:00:00.000Z' },
}

Is there a reason why the mockImplementation isn't working? Is there an easier more straightforward way to do this?

Tried a bunch of things including:

        const spy = jest.spyOn(global, 'Date')
        const date = spy.mock.instances[0]

        const queryMocked = {
            expected: { $lte: date },
        }

I am getting: Property 'setSystemTime' does not exist on type 'typeof jest'.

I think it's one of the solutions I've tried, but I didn't mention it, because it's also the first one that failed.

Upvotes: 0

Views: 3270

Answers (1)

absolutezero
absolutezero

Reputation: 124

The mock for Date.now should look like

Date.now = jest.fn(() => 1606348800)

You can also use a fake timer, provided by jest

jest
  .setSystemTime(new Date('2020-01-01'));

This post may provide additional help

Upvotes: 2

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