A bug that only appears once a year

There are some bugs that only appear under certain circumstances. Today was the day I’ve got one of those (there is a hint in this sentence).

I pushed a small change and got a red build as a result. I already had the corresponding test fixed so red build was not something I was expecting.

An exception I’ve got was from a check in TicketTransferPolicy which had nothing at all to do with my changes. And so the investigation began.

raise DeadlinePassed  if deadline_passed?(event)
def deadline_passed?(event)
  if FT.on?(:extended_tickets_transfer_deadline, organizer_id: event.user_id)
    event.ends_at < Time.current
    event.starts_at < Time.current.advance(days: 1)

Hint: failing test was not related to extended deadline.

I’ve looked into the failing test and here’s the line that instantly got my attention:

event = test_organizer.create_published_event(starts_at: 25.hours.from_now)

This was an instant ‘aha’ moment when I’ve realized, today’s the day when we have 25 hours in the day.

In my opinion, the best solution here is to use Time.current.advance(days: 1, hours: 1) in the test instead of 25.hours.from_now, this approach is more consistent with the code we’re testing. Changing 25 to 26 would also work ;)

Thanks, DST :P

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