Although many great answers were written to this question, none of them uses the Rspec tags
approach.
I use tags to run one or more specs in different files -- only those related to my current development task.
For example, I add the tag "dev" with the value "current":
it "creates an user", dev: :current do
user = create(:user)
expect(user.persisted?).to be_truthy
end
then I run
bundle exec rspec . --tag dev:current
Different tags/values can be set in individual specs or groups.