How to properly mock moment.js helper function

[yevhendevbox]

Hey, still struggling with unit tests, now i am testing the component which is using some utility function (moment js converter), how do i properly mock it, to prevent of getting this error:

Deprecation warning: value provided is not in a recognized RFC2822 or ISO format. moment construction falls back to js Date(), which is not reliable across all browsers and versions. Non RFC2822/ISO date formats are discouraged. Please refer to http://momentjs.com/guides/#/warnings/js-date/ for more info.
Arguments: 
[0] _isAMomentObject: true, _isUTC: false, _useUTC: false, _l: undefined, _i: some date, _f: undefined, _strict: undefined, _locale: [object Object]

component template:

 <div class="projects-list__col col-other">
      <span>{{ displayRelativeTimeFilter(props.site.last_modified_at) }}</span>
    </div>

filter function:

import moment from 'moment'

export function displayRelativeTimeFilter(timeStamp: string): string {
  return moment(timeStamp).fromNow()
}

test case:

 const wrapper = shallowMount(SiteCard, {
    props: {
      site: {
        id: 1,
        domain: null,
        is_init: true,
        name: 'site1',
        subdomain: null,
        trashed: false,
        url: 'https://site1.com',
        created_at: 'some date',
        last_modified_at: 'some date'
      }
    },
    global: {
      stubs: {
        RouterLink: RouterLinkStub
      }
    }
  })

  test('should renders properly', () => {
    vi.doMock('@/utils/filters/displayRelativeTimeFilter.ts', () => {
      return {
        displayRelativeTimeFilter: vi.fn().mockReturnValue('4 days from now')
      }
    })
    expect(wrapper.exists()).toBeTruthy()
  })

Certainly i am doing some thing incorrect, any tips highly appreciate!

[cexbrayat]

I don't think this has anything to do with Vue Test Utils, but the mock probably needs to be declared before mounting the component. I usually use vi.mock but that should work with doMock as well.

In the future, if you want help, please add a small repro online using https://stackblitz.com/github/vuejs/create-vue-templates/tree/main/typescript-vitest?file=src%2Fcomponents%2F__tests__%2FHelloWorld.spec.ts but keep the questions focused on Vue Test Utils