CircleCI with Rails server and ember app

I'm working on a Rails application, that uses ember as front-end framework for the client side within the application. I use Capybara on CircleCI to run the tests.

I have a lot of end-to-end tests, which make the build time very slow. I have found that the problem could be because it builds ember application for every spec file separately.

Is there anyone who knows if I can build the whole application once (somehow), and use that as the test server, to speed up the build. Or some other method/suggestion to improve the speed of my build.

Thanks