Add Test For A Subset Of Attributes On A Model as a Rails TIL

rails/test-for-a-subset-of-attributes-on-a-model.md

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+# Test For A Subset Of Attributes On A Model
+
+Let's say you are using RSpec to test some code that creates or updates an
+ActiveRecord object. To evaluate that the code is working, you want to check
+the value of a couple different attributes. Though you could have a series of
+assert statements to check each value, you may want to combine them into a
+single statement.
+
+```ruby
+book = process_that_updates_book(params)
+
+expect(book.attributes).to match(
+  "title" => 'Updated title',
+  "publication_year" => 2001,
+  # ... you have to check *every* attribute
+)
+```
+
+The `#match` matcher requires that every attribute in the hash matches. We
+don't really care to check the `created_at`, `updated_at`, and other irrelevant
+attributes.
+
+Instead, we can `match` on
+[`hash_including`](https://rubydoc.info/gems/rspec-mocks/RSpec%2FMocks%2FArgumentMatchers:hash_including).
+Additionally, we can `symbolize_keys` on the `attributes` to make the expected
+data a little cleaner.
+
+```ruby
+book = process_that_updates_book(params)
+
+expect(book.attributes).to match(hash_including(
+  title: 'Updated title',
+  publication_year: 2001,
+))
+```
+
+If the specified attributes match, then the expectation will pass. If at least
+one of them doesn't, then it will fail. All other attributes are ignored.