Only run rails 4 tests a single time from the command line

lib/jasmine_rails/offline_asset_paths.rb

@@ -25,7 +25,13 @@ def compute_public_path_with_offline_asset(source, dir, options={})
 
       FileUtils.mkdir_p File.dirname(source_path)
       Rails.logger.debug "Compiling #{source} to #{source_path}"
-      File.open(source_path, 'w') {|f| f << content }
+      File.open(source_path, 'w') do |f|
+        if Rails::VERSION::MAJOR == 4 && !Rails.env.test? && source == 'jasmine-specs.js'
+          f << ''
+        else
+          f << content
+        end
+      end
       "/assets/#{source}"
     end