How do you run a single test/spec file in RSpec?

The raw invocation:

rake spec SPEC=spec/controllers/sessions_controller_spec.rb \
          SPEC_OPTS="-e \"should log in with cookie\""

Now figure out how to embed this into your editor.

Or you can skip rake and use the 'rspec' command:

bundle exec rspec path/to/spec/file.rb

In your case I think as long as your ./spec/db_spec.rb file includes the appropriate helpers, it should work fine.

If you're using an older version of rspec it is:

bundle exec spec path/to/spec/file.rb