Unit Test for Timespan with Javascript

I would like to write a Unit Test for my Timespan. I got some more lines of Code for Week,Year,Quartal. But if i know how to Test "Today and Yesterday, i could use them for the others too. Hope someone can help me :)

const firstSelectionOptions = {
  [Timespan.Day]: [
    { value: FirstSelection.Current, name: 'Today' },
    { value: FirstSelection.Previous, name: 'Yesterday' },
  ]