Rspec - Check if an array have same elements than other, regardless of the order

Question

I'm not sure if its a Rspec question, but I only encountred this problem on Rspec tests.

I want to check if an array is equal to another array, regardless of the elements order :

[:b, :a, :c] =?= [:a, :b, :c]

My current version :

my_array.length.should == 3
my_array.should include(:a)
my_array.should include(:b)
my_array.should include(:c)

Is there any method on Rspec, ruby or Rails for do something like this :

my_array.should have_same_elements_than([:a, :b, :c])

Regards

Similar to [Rspec: “array.should == another_array” but without concern for order](http://stackoverflow.com/q/2978922/567863) — Paul Fioravanti, Apr 10 '13 at 12:23

score 36 · Answer 1 · answered Apr 10 '13 at 12:19

36

There is a match_array matcher in RSpec which does this:

http://rubydoc.info/github/rspec/rspec-expectations/RSpec/Matchers:match_array

answered Apr 10 '13 at 12:19

Andy Waite

10,785
4
33
47

damn, didn't know that, +1 – apneadiving Apr 10 '13 at 12:20
Best solution for many people, but I can't install RSpec > 2.11. – pierallard Apr 10 '13 at 12:47
`contain_exactly` does the trick as well, for a splatted array (see https://stackoverflow.com/a/48206163/6320039) – Ulysse BN Jun 27 '18 at 10:23

Stefan · Answer 2 · 2014-08-16T10:53:46.937

You can use the =~ operator:

[:b, :a, :c].should =~ [:a, :b, :c] # pass

From the docs:

Passes if actual contains all of the expected regardless of order. This works for collections. Pass in multiple args and it will only pass if all args are found in collection.

For RSpec's expect syntax there's match_array:

expect([:b, :a, :c]).to match_array([:a, :b, :c]) # pass

or contain_exactly if you're passing single elements:

expect([:b, :a, :c]).to contain_exactly(:a, :b, :c) # pass

score 3 · Answer 3 · answered Apr 10 '13 at 12:16

3

This should work.

[:b, :a, :c].sort == [:a, :b, :c].sort

answered Apr 10 '13 at 12:16

Missing a `should`. In any case, @Stefan has the right answer. – Marc-André Lafortune Apr 10 '13 at 13:55

score 3 · Answer 4 · answered Jan 11 '18 at 11:37

I think all answers seems to be pretty old. Latest matcher is contain_exactly.

You can simply do -

expect([:b, :a, :c]).to contain_exactly(:a, :b, :c)

Please not that in contain_exactly we don't pass a whole array, instead pass separate elements.

Ref - Rspec Guide

apneadiving · Accepted Answer · 2013-04-10T13:07:13.787

2

Here was my wrong matcher (thanks @steenslag):

RSpec::Matchers.define :be_same_array_as do |expected_array|
  match do |actual_array|
    (actual_array | expected_array) - (actual_array & expected_array) == []
  end
end

Other solutions:

use the builtin matcher, best solution
use Set:

Something like:

require 'set'
RSpec::Matchers.define :be_same_array_as do |expected_array|
  match do |actual_array|
    Set.new(actual_array) == Set.new(expected_array)
  end
end

edited Apr 10 '13 at 13:07

answered Apr 10 '13 at 12:14

apneadiving

114,565
26
219
213

What an elegant solution ! Thanks ! I knew `&`, but you learned me the operator `|`. – pierallard Apr 10 '13 at 12:18
I didn't downvote, but this fails when there are duplicates: [3,2,1,1] and [1,2,3] returns true. – steenslag Apr 10 '13 at 12:35
@steenslag: `([3,2,1,1] | [1,2,3] - [3,2,1,1] & [1,2,3]) => [3, 2, 1]` and `([1,2 ,3] | [3, 2, 1, 1] - [1, 2, 3] & [3, 2, 1, 1])=> [1, 2, 3]` this doesn't return true since it's different from `[]` – apneadiving Apr 10 '13 at 12:38
`spec/support/custom_matchers.rb` is where I store this – apneadiving Apr 10 '13 at 12:47
@apneadiving In your post you are doing `([3,2,1,1] | [1,2,3]) - ([3,2,1,1] & [1,2,3])` which is different from your comment (result: []) – steenslag Apr 10 '13 at 12:49
@apneadiving [3,2,1,1] and [1,2,3,2] still failing. I guess this is why Array does not have a `^` method like Set . – steenslag Apr 10 '13 at 13:03
@steenslag: you've made my day :) – apneadiving Apr 10 '13 at 13:04
2

There is no need to go through all this. Just use the builtin operator `=~` like in Stefan's answer. – Nick Messick Apr 10 '13 at 19:25
The answer includes two custom matchers, which is extremely bad practice when a builtin operator is available. – Nick Messick Apr 10 '13 at 19:34
@messick: yes I didn't delete my first anser ubt I wrote `use the builtin matcher, best solution` what else do you need? – apneadiving Apr 10 '13 at 19:36
Downvote because: The answer is very NOT straightforward. Users tend to read quickly, and won't see your _best solution_ part. Plus It is unclear. – Ulysse BN Jun 27 '18 at 10:24

Rspec - Check if an array have same elements than other, regardless of the order

5 Answers5