How to run local commands like 'npm test' with Capistrano

Before I deploy, I want to run my test suite locally (executed with npm test). I also want the deployment to stop if the tests fail.

I created a new file in lib/capistrano/tasks. I called it test.rake. Here are the contents:

namespace :test do
  desc 'Run Tests'
  task :run do
    run_locally do
      unless system 'npm test'
        puts 'Test(s) failed, so the deployment is being aborted.'

        exit;
      end
    end
  end
end

Then, in my deploy.rb deploy block, I run the command like this:

before :starting, 'test:run'