Why my DateTime format changed on Bamboo build - ruby-on-rails

Question

I have a User class that has_many Jobs. I map jobs with the following code, the start_at and end_at are datetime:
def ranges
user.jobs.map { |u| [u.start_at, u.end_at] }
end
I have a spec that compares two arrays:
my_array = [[start1, end1], [start2, end2]]
expect(ranges).to eq my_array
The test data are also datetime created from factory girl e.g.
create(:jobs, start_at:DateTime.parse('2017-03-26 00:00:00'), end_at: DateTime.parse('2017-03-27 00:00:00'))
Everything works fine, expect when Bamboo runs my spec, I get following error:
expect
[[2017-12-31 00:00:00.000000000 +0000, 2017-12-31 10:10:00.000000000 +0000], [2017-12-30 00:00:00.000000000 +0000, 2017-12-31 00:10:00.000000000 +0000], [2017-11-26 00:00:00.000000000 +0000, 2017-11-26 10:10:00.000000000 +0000], [2017-03-24 00:00:00.000000000 +0000, 2017-03-24 10:10:00.000000000 +0000], [2017-03-25 00:00:00.000000000 +0000, 2017-03-25 10:10:00.000000000 +0000], [2017-03-26 00:00:00.000000000 +0000, 2017-03-26 10:10:00.000000000 +0000]]
to match
[[Sun, 26 Mar 2017 00:00:00 UTC +00:00, Sun, 26 Mar 2017 10:10:00 UTC +00:00], [Sat, 25 Mar 2017 00:00:00 UTC +00:00, Sat, 25 Mar 2017 10:10:00 UTC +00:00], [Fri, 24 Mar 2017 00:00:00 UTC +00:00, Fri, 24 Mar 2017 10:10:00 UTC +00:00], [Sun, 26 Nov 2017 00:00:00 UTC +00:00, Sun, 26 Nov 2017 10:10:00 UTC +00:00], [Sat, 30 Dec 2017 00:00:00 UTC +00:00, Sun, 31 Dec 2017 00:10:00 UTC +00:00], [Sun, 31 Dec 2017 00:00:00 UTC +00:00, Sun, 31 Dec 2017 10:10:00 UTC +00:00]]
dose this mean I need to format all my datetime object byiso8601 all the time? what could cause this on Bamboo

Answer 1

The problem isn't your format. The problem is that the array elements are not in the same order. The dates in your expect array begin with the 2017-12-31 dates, while those in your match array begin with the 2017-03-26 dates.
RSpec's eq method returns true only if each element of the first array is identical to the element at the same index of the second array. But the match_array method returns true so long as the two arrays have the same elements, regardless of order.
Change your expectation line to:
expect(ranges).to match_array(my_array)
And you should be good to go.