Encourage `specify` instead of `it do`

For empty test blocks

doc/development/testing_guide/best_practices.md

@@ -70,6 +70,7 @@ When using spring and guard together, use `SPRING=1 bundle exec guard` instead t
   use a Capyabara matcher beforehand (e.g. `find('.js-foo')`) to ensure the element actually exists.
 - Use `focus: true` to isolate parts of the specs you want to run.
 - Use [`:aggregate_failures`](https://relishapp.com/rspec/rspec-core/docs/expectation-framework-integration/aggregating-failures) when there is more than one expectation in a test.
+- For [empty test description blocks](https://github.com/rubocop-hq/rspec-style-guide#it-and-specify), use `specify` rather than `it do` if the test is self-explanatory.
 
 ### System / Feature tests