fix minor issues

.simplecov_spawn.rb

@@ -1,9 +1,11 @@
-unless ENV["COVERAGE"] && ENV["COVERAGE"].empty?
+# frozen_string_literal: true
+
+unless ENV['COVERAGE'] && ENV['COVERAGE'].empty?
   require 'simplecov'
   require 'simplecov-cobertura'
 
   SimpleCov.command_name 'spawn'
   SimpleCov.at_fork.call(Process.pid)
   SimpleCov.formatter SimpleCov::Formatter::CoberturaFormatter
   SimpleCov.start
-end
+end

Gemfile

@@ -10,9 +10,9 @@ gem 'roda'
 gem 'rspec-rails'
 
 group :test do
-  gem 'super_diff'
   gem 'simplecov'
   gem 'simplecov-cobertura'
+  gem 'super_diff'
 end
 
 group :development do