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.

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. Additionally, we can symbolize_keys on the attributes to make the expected data a little cleaner.

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.