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I have this cypress test where Im checking for a correct billing date. Our website has monthly subscriptions and it works as follows: If you start your subscription on January 31st, your next billing date will automatically be on the 1st of March since February has only 28 days. Same if you start your subscription on the 31st of March, then your next billing date will be on the first of 1st of May since there is no 31st in April and it automatically changes to the first day of the next month. Starting on other normal dates like the 15th will always be the same date (15th) of the next month etc..

My issue is when testing this with cypress, i always get the last day of the next month. For example if i test that Im gonna start my subscription on the 31st of March, my test will have 30th of April as an expected result, which is not correct since i want the expected result of my test to be 1st of May.

I am using this function but i cant seem to make it work properly since there are many differences in the months.

export const getBillingDate = (todayDate: string, months: number) => {
  const date1 = new Date(todayDate)
  const date2 = new Date(todayDate)
  date1.setDate(1)
  const daysInNextMonth = getDaysInMonth(addMonths(date1, months))
  date2.setDate(Math.min(date2.getDate(), daysInNextMonth))
  return format(addMonths(date2, months), 'MMMM do, yyyy')
}

I would really appreciate anyone's help with this since i am new to Cypress and testing in general. (Sorry english is not my first language)

Mimz
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  • What is the exact date format of the start billing date and next billing date. – Alapan Das Mar 31 '22 at 15:43
  • @AlapanDas Actually on our platform it shows the date like this: "Your next bill is for €13.99 on May 1st, 2022". But Im using another function in my cypress test : " const billingDate = getBillingDate(new Date().toString(), 1) " to convert the date to a string so i can check that the text is correct. – Mimz Mar 31 '22 at 15:55
  • Probably a duplicate of [*JavaScript function to add X months to a date*](https://stackoverflow.com/questions/2706125/javascript-function-to-add-x-months-to-a-date) – RobG Mar 31 '22 at 22:37

4 Answers4

1

Both dayjs and javascript new Date() fail to add all the dates exactly as you want.

But you can use dayjs().daysInMonth() to get results exactly as per your description,

const getBilling = (startDate) => {
  const [year, month, day] = startDate.split('/')

  const sd = dayjs(startDate)
  const firstOfNextMonth = sd.month(sd.month() + 1).date(1)
  const daysInNextMonth = dayjs(firstOfNextMonth).daysInMonth()

  let end;
  if (daysInNextMonth < day) {
    end = `${year}/${+month+2}/${1}`  // always bump to 1st day of month + 2
  } else {
    end = `${year}/${+month+1}/${day}`
  }

  return dayjs(end, 'YYYY/MM/DD').format('YYYY/MM/DD')
}

it('gets billing date, accounting for short months', () => {

  //Jan
  expect(getBilling('2022/01/15')).to.eq('2022/02/15')
  expect(getBilling('2022/01/31')).to.eq('2022/03/01')

  //Feb
  expect(getBilling('2022/02/15')).to.eq('2022/03/15')
  expect(getBilling('2022/02/28')).to.eq('2022/03/28')

  //Mar
  expect(getBilling('2022/03/15')).to.eq('2022/04/15')
  expect(getBilling('2022/03/31')).to.eq('2022/05/01')

})

enter image description here

Fody
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  • Thank you so much! This worked exactly like i wanted it to. I appreciate your help. – Mimz Apr 01 '22 at 12:17
0

Day.js already exists to do date math.

You can use their .add() to add 30 days to a date dayjs().add(30, 'day').

You can also format the dates with .format() to format the way you want it dayjs('2019-01-25').format('DD/MM/YYYY') // '25/01/2019'

jjhelguero
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  • Thank you! But how will this look if today is the 31st of January and Im going to add 30 days? Since February can only have 28 or 29? – Mimz Mar 31 '22 at 16:05
  • I imagine day.js takes into account the leap year days. If your billing dates are 30 days or a month then you can add that edge case for FEb. – jjhelguero Mar 31 '22 at 16:30
  • @jjhelguero—hardly an "edge case", it happens frequently. – RobG Mar 31 '22 at 22:39
0

Your requirements are a little unusual. Typically when adding a month and it overflows, the requirement is to return the last day of the month, not the first of the following month. But it's not difficult, just get the starting date (day in month), add a month, and if the resulting date isn't the same, set it to the 1st, e.g.:

function addBillingMonth(date = new Date()) {
  let d = new Date(+date);
  let dayNum = d.getDate();
  d.setMonth(d.getMonth() + 1);
  if (dayNum !== d.getDate()) {
    d.setDate(1);
  }
  return d;
}

// Examples
[ new Date(2021,11,31), // 31 Dec
  new Date(2022, 0,15), // 15 Jan
  new Date(2022, 0,31), // 31 Jan
  new Date(2022, 2,31), // 31 Mar
].forEach(d => console.log(d.toDateString() +
  ' next bill: ' + addBillingMonth(d).toDateString())
);
RobG
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0

You have a months parameter, if you want to increase by more that one month you should calculate each month separately.

'dayjs` definitely gives you more options to play with.

const expect = chai.expect

const addBillingMonth = (start) => {
  let next = start.add(1, 'month')
  if (start.date() !== next.date()) {
    next = next.add(1, 'month').startOf('month')
  }
  return next  
}

const getBilling = (startDate, months = 1) => {
  let result = dayjs(startDate)
  for (let i = 0; i < months; i++) {
    result = addBillingMonth(result)  // repeat for each month
  }
  return result.format('YYYY/MM/DD')
}

expect(getBilling('2022/01/15')).to.eq('2022/02/15')
expect(getBilling('2022/01/31')).to.eq('2022/03/01')
expect(getBilling('2022/02/15')).to.eq('2022/03/15')
expect(getBilling('2022/02/28')).to.eq('2022/03/28')
expect(getBilling('2022/03/15')).to.eq('2022/04/15')
expect(getBilling('2022/03/31')).to.eq('2022/05/01')
<script src="https://cdnjs.cloudflare.com/ajax/libs/chai/4.3.6/chai.min.js"></script>
<script src="https://unpkg.com/dayjs@1.8.21/dayjs.min.js"></script>
TesterDick
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