How to assert list of values in ascending order?












0















Here is a list of values in an array:



[463, 246, 216, 194, 154, 152, 147, 140, 129, 128, 123, 118, 118, 102, 102, 101, 97, 96, 93, 85]


How can I ensure/assert through RSpec that the array list is in ascending order?






ruby rspec







share|improve this question




















  • 3





    list == list.sort?

    – Aleksei Matiushkin
    May 31 '17 at 7:13











  • Providing an example in a question is generally helpful, but the inclusion of an arbitrary numeric array that is not referenced by the question serves no purpose.

    – Cary Swoveland
    May 31 '17 at 7:44
















0















Here is a list of values in an array:



[463, 246, 216, 194, 154, 152, 147, 140, 129, 128, 123, 118, 118, 102, 102, 101, 97, 96, 93, 85]


How can I ensure/assert through RSpec that the array list is in ascending order?






ruby rspec







share|improve this question




















  • 3





    list == list.sort?

    – Aleksei Matiushkin
    May 31 '17 at 7:13











  • Providing an example in a question is generally helpful, but the inclusion of an arbitrary numeric array that is not referenced by the question serves no purpose.

    – Cary Swoveland
    May 31 '17 at 7:44














0












0








0








Here is a list of values in an array:



[463, 246, 216, 194, 154, 152, 147, 140, 129, 128, 123, 118, 118, 102, 102, 101, 97, 96, 93, 85]


How can I ensure/assert through RSpec that the array list is in ascending order?






ruby rspec







share|improve this question
















Here is a list of values in an array:



[463, 246, 216, 194, 154, 152, 147, 140, 129, 128, 123, 118, 118, 102, 102, 101, 97, 96, 93, 85]


How can I ensure/assert through RSpec that the array list is in ascending order?






ruby rspec




ruby rspec






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Jun 5 '17 at 14:52







Prashanth Sams

















asked May 31 '17 at 7:10









Prashanth SamsPrashanth Sams

7,13685176




7,13685176








  • 3





    list == list.sort?

    – Aleksei Matiushkin
    May 31 '17 at 7:13











  • Providing an example in a question is generally helpful, but the inclusion of an arbitrary numeric array that is not referenced by the question serves no purpose.

    – Cary Swoveland
    May 31 '17 at 7:44














  • 3





    list == list.sort?

    – Aleksei Matiushkin
    May 31 '17 at 7:13











  • Providing an example in a question is generally helpful, but the inclusion of an arbitrary numeric array that is not referenced by the question serves no purpose.

    – Cary Swoveland
    May 31 '17 at 7:44








3




3





list == list.sort?

– Aleksei Matiushkin
May 31 '17 at 7:13





list == list.sort?

– Aleksei Matiushkin
May 31 '17 at 7:13













Providing an example in a question is generally helpful, but the inclusion of an arbitrary numeric array that is not referenced by the question serves no purpose.

– Cary Swoveland
May 31 '17 at 7:44





Providing an example in a question is generally helpful, but the inclusion of an arbitrary numeric array that is not referenced by the question serves no purpose.

– Cary Swoveland
May 31 '17 at 7:44












2 Answers
2






active

oldest

votes


















6














The simplest way is probably:



expect(array.sort).to eq(array)





share|improve this answer





















  • 1





    To assert that it is in strictly ascending order, add a separate test expect(array.uniq.size) == array.size.

    – Cary Swoveland
    May 31 '17 at 7:18











  • Yes @IIya that makes sense :)

    – Prashanth Sams
    May 31 '17 at 7:30






  • 1





    Array#sort is not stable, so this does not work if there are equal elements.

    – Jörg W Mittag
    May 31 '17 at 10:34






  • 2





    Array#sort is stable in the context of this question (array of ints).

    – Ilya
    May 31 '17 at 10:48





















1














"Ascending" means "the next element is not smaller than the current". You can encode that into a predicate easily:



expect(array.each_cons(2).all? {|a, b| a <= b }).to be_truthy


Note that Array#sort is not stable, so something like 



expect(array.sort).to eq(array)


does not work!






share|improve this answer
























  • Could you please provide an instance, when sort does not work, but your answer works? Also, be_truthy is not nil or false, be true is enough.

    – Ilya
    May 31 '17 at 10:39













  • sort is unstable, which means that if there are elements where <=> returns 0, there is no guarantee that they will keep their relative order. There is also no guarantee that for elements where <=> returns 0, == returns true (although I would consider that very strange if not a bug, but hey, people do strange things). So, if there are two elements which have the same order but are not equal, then they may get swapped by sorting and resulting in the original array and the sorted array to not be equal.

    – Jörg W Mittag
    May 31 '17 at 10:43






  • 1





    But there are only integers in the question, I think your answer is overhead in this context, but, of course, makes sense in some (very rare) conditions.

    – Ilya
    May 31 '17 at 10:47











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









6














The simplest way is probably:



expect(array.sort).to eq(array)





share|improve this answer





















  • 1





    To assert that it is in strictly ascending order, add a separate test expect(array.uniq.size) == array.size.

    – Cary Swoveland
    May 31 '17 at 7:18











  • Yes @IIya that makes sense :)

    – Prashanth Sams
    May 31 '17 at 7:30






  • 1





    Array#sort is not stable, so this does not work if there are equal elements.

    – Jörg W Mittag
    May 31 '17 at 10:34






  • 2





    Array#sort is stable in the context of this question (array of ints).

    – Ilya
    May 31 '17 at 10:48


















6














The simplest way is probably:



expect(array.sort).to eq(array)





share|improve this answer





















  • 1





    To assert that it is in strictly ascending order, add a separate test expect(array.uniq.size) == array.size.

    – Cary Swoveland
    May 31 '17 at 7:18











  • Yes @IIya that makes sense :)

    – Prashanth Sams
    May 31 '17 at 7:30






  • 1





    Array#sort is not stable, so this does not work if there are equal elements.

    – Jörg W Mittag
    May 31 '17 at 10:34






  • 2





    Array#sort is stable in the context of this question (array of ints).

    – Ilya
    May 31 '17 at 10:48
















6












6








6







The simplest way is probably:



expect(array.sort).to eq(array)





share|improve this answer















The simplest way is probably:



expect(array.sort).to eq(array)






share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 26 '18 at 4:43

























answered May 31 '17 at 7:13









IlyaIlya

11.5k42441




11.5k42441








  • 1





    To assert that it is in strictly ascending order, add a separate test expect(array.uniq.size) == array.size.

    – Cary Swoveland
    May 31 '17 at 7:18











  • Yes @IIya that makes sense :)

    – Prashanth Sams
    May 31 '17 at 7:30






  • 1





    Array#sort is not stable, so this does not work if there are equal elements.

    – Jörg W Mittag
    May 31 '17 at 10:34






  • 2





    Array#sort is stable in the context of this question (array of ints).

    – Ilya
    May 31 '17 at 10:48
















  • 1





    To assert that it is in strictly ascending order, add a separate test expect(array.uniq.size) == array.size.

    – Cary Swoveland
    May 31 '17 at 7:18











  • Yes @IIya that makes sense :)

    – Prashanth Sams
    May 31 '17 at 7:30






  • 1





    Array#sort is not stable, so this does not work if there are equal elements.

    – Jörg W Mittag
    May 31 '17 at 10:34






  • 2





    Array#sort is stable in the context of this question (array of ints).

    – Ilya
    May 31 '17 at 10:48










1




1





To assert that it is in strictly ascending order, add a separate test expect(array.uniq.size) == array.size.

– Cary Swoveland
May 31 '17 at 7:18





To assert that it is in strictly ascending order, add a separate test expect(array.uniq.size) == array.size.

– Cary Swoveland
May 31 '17 at 7:18













Yes @IIya that makes sense :)

– Prashanth Sams
May 31 '17 at 7:30





Yes @IIya that makes sense :)

– Prashanth Sams
May 31 '17 at 7:30




1




1





Array#sort is not stable, so this does not work if there are equal elements.

– Jörg W Mittag
May 31 '17 at 10:34





Array#sort is not stable, so this does not work if there are equal elements.

– Jörg W Mittag
May 31 '17 at 10:34




2




2





Array#sort is stable in the context of this question (array of ints).

– Ilya
May 31 '17 at 10:48







Array#sort is stable in the context of this question (array of ints).

– Ilya
May 31 '17 at 10:48















1














"Ascending" means "the next element is not smaller than the current". You can encode that into a predicate easily:



expect(array.each_cons(2).all? {|a, b| a <= b }).to be_truthy


Note that Array#sort is not stable, so something like 



expect(array.sort).to eq(array)


does not work!






share|improve this answer
























  • Could you please provide an instance, when sort does not work, but your answer works? Also, be_truthy is not nil or false, be true is enough.

    – Ilya
    May 31 '17 at 10:39













  • sort is unstable, which means that if there are elements where <=> returns 0, there is no guarantee that they will keep their relative order. There is also no guarantee that for elements where <=> returns 0, == returns true (although I would consider that very strange if not a bug, but hey, people do strange things). So, if there are two elements which have the same order but are not equal, then they may get swapped by sorting and resulting in the original array and the sorted array to not be equal.

    – Jörg W Mittag
    May 31 '17 at 10:43






  • 1





    But there are only integers in the question, I think your answer is overhead in this context, but, of course, makes sense in some (very rare) conditions.

    – Ilya
    May 31 '17 at 10:47
















1














"Ascending" means "the next element is not smaller than the current". You can encode that into a predicate easily:



expect(array.each_cons(2).all? {|a, b| a <= b }).to be_truthy


Note that Array#sort is not stable, so something like 



expect(array.sort).to eq(array)


does not work!






share|improve this answer
























  • Could you please provide an instance, when sort does not work, but your answer works? Also, be_truthy is not nil or false, be true is enough.

    – Ilya
    May 31 '17 at 10:39













  • sort is unstable, which means that if there are elements where <=> returns 0, there is no guarantee that they will keep their relative order. There is also no guarantee that for elements where <=> returns 0, == returns true (although I would consider that very strange if not a bug, but hey, people do strange things). So, if there are two elements which have the same order but are not equal, then they may get swapped by sorting and resulting in the original array and the sorted array to not be equal.

    – Jörg W Mittag
    May 31 '17 at 10:43






  • 1





    But there are only integers in the question, I think your answer is overhead in this context, but, of course, makes sense in some (very rare) conditions.

    – Ilya
    May 31 '17 at 10:47














1












1








1







"Ascending" means "the next element is not smaller than the current". You can encode that into a predicate easily:



expect(array.each_cons(2).all? {|a, b| a <= b }).to be_truthy


Note that Array#sort is not stable, so something like 



expect(array.sort).to eq(array)


does not work!






share|improve this answer













"Ascending" means "the next element is not smaller than the current". You can encode that into a predicate easily:



expect(array.each_cons(2).all? {|a, b| a <= b }).to be_truthy


Note that Array#sort is not stable, so something like 



expect(array.sort).to eq(array)


does not work!







share|improve this answer












share|improve this answer



share|improve this answer










answered May 31 '17 at 10:34









Jörg W MittagJörg W Mittag

294k63359557




294k63359557













  • Could you please provide an instance, when sort does not work, but your answer works? Also, be_truthy is not nil or false, be true is enough.

    – Ilya
    May 31 '17 at 10:39













  • sort is unstable, which means that if there are elements where <=> returns 0, there is no guarantee that they will keep their relative order. There is also no guarantee that for elements where <=> returns 0, == returns true (although I would consider that very strange if not a bug, but hey, people do strange things). So, if there are two elements which have the same order but are not equal, then they may get swapped by sorting and resulting in the original array and the sorted array to not be equal.

    – Jörg W Mittag
    May 31 '17 at 10:43






  • 1





    But there are only integers in the question, I think your answer is overhead in this context, but, of course, makes sense in some (very rare) conditions.

    – Ilya
    May 31 '17 at 10:47



















  • Could you please provide an instance, when sort does not work, but your answer works? Also, be_truthy is not nil or false, be true is enough.

    – Ilya
    May 31 '17 at 10:39













  • sort is unstable, which means that if there are elements where <=> returns 0, there is no guarantee that they will keep their relative order. There is also no guarantee that for elements where <=> returns 0, == returns true (although I would consider that very strange if not a bug, but hey, people do strange things). So, if there are two elements which have the same order but are not equal, then they may get swapped by sorting and resulting in the original array and the sorted array to not be equal.

    – Jörg W Mittag
    May 31 '17 at 10:43






  • 1





    But there are only integers in the question, I think your answer is overhead in this context, but, of course, makes sense in some (very rare) conditions.

    – Ilya
    May 31 '17 at 10:47

















Could you please provide an instance, when sort does not work, but your answer works? Also, be_truthy is not nil or false, be true is enough.

– Ilya
May 31 '17 at 10:39







Could you please provide an instance, when sort does not work, but your answer works? Also, be_truthy is not nil or false, be true is enough.

– Ilya
May 31 '17 at 10:39















sort is unstable, which means that if there are elements where <=> returns 0, there is no guarantee that they will keep their relative order. There is also no guarantee that for elements where <=> returns 0, == returns true (although I would consider that very strange if not a bug, but hey, people do strange things). So, if there are two elements which have the same order but are not equal, then they may get swapped by sorting and resulting in the original array and the sorted array to not be equal.

– Jörg W Mittag
May 31 '17 at 10:43





sort is unstable, which means that if there are elements where <=> returns 0, there is no guarantee that they will keep their relative order. There is also no guarantee that for elements where <=> returns 0, == returns true (although I would consider that very strange if not a bug, but hey, people do strange things). So, if there are two elements which have the same order but are not equal, then they may get swapped by sorting and resulting in the original array and the sorted array to not be equal.

– Jörg W Mittag
May 31 '17 at 10:43




1




1





But there are only integers in the question, I think your answer is overhead in this context, but, of course, makes sense in some (very rare) conditions.

– Ilya
May 31 '17 at 10:47





But there are only integers in the question, I think your answer is overhead in this context, but, of course, makes sense in some (very rare) conditions.

– Ilya
May 31 '17 at 10:47


















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