How to mock distinctUntilChanged in an angular app

[tomavic]

Is your feature request related to a problem? Please describe.
I need to mock the following:

  getListOfItems() {
    // When Filter or Language changes
    return merge(
      this.translate.onLangChange,
      this.storeService.filtration$.pipe(
        distinctUntilChanged(
          (prev, curr) =>
            prev.searchKey === curr.searchKey &&
            prev.pageNumber === curr.pageNumber &&
            prev.pageSize === curr.pageSize &&
            prev.filterKey === curr.filterKey
        )
      )
    ).pipe(switchMap(() => this.getBundlesList()));
  }

Additional context
Angular app