Add Comparing Arrays In RSpec as a ruby til.

ruby/comparing-arrays-in-rspec.md

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+# Comparing Arrays In RSpec
+
+Among its many built-in matchers, RSpec includes a set of array matchers.
+One of the array matchers is `match_array` which compares two arrays
+independent of ordering. This is handy if you need to check that a resulting
+array matches your expectations when ordering is unimportant and not
+necessarily deterministic. It can be used like so:
+
+```ruby
+expect([1,2,3]).to match_array([3,2,1])
+```
+
+This expectation is met, the test will pass.