Prefer match_array or contain_exactly over eq

When checking the contents of an Enumerable where the order doesnt matter, prefer RSpec’s match_array or contain_exactly over eq.

This practice help us avoid brittle test suites where a code change may result in a different, but inconsequential, re-ordering of a function’s results.

Bad 🔗

In this example, using eq makes an assumption about the behavior of the User#interests function as it relates to the order of add_interest function calls. This is brittle if User#interests is changed to return this list in a different order.

user.add_interest(interest_a)
user.add_interest(interest_b)
user.add_interest(interest_c)
expect(user.interests).to eq([interest_a, interest_b, interest_c])

Good 🔗

Use match_array or contain_exactly when the order of of a function’s results could be ambiguous.

user.add_interest(interest_a)
user.add_interest(interest_b)
user.add_interest(interest_c)
expect(user.interests).to match_array([interest_a, interest_b, interest_c])

user.add_interest(interest_a)
user.add_interest(interest_b)
user.add_interest(interest_c)
expect(user.interests).to contain_exactly(interest_a, interest_b, interest_c)