test: Setup coverage

spec/rails_helper.rb

@@ -4,6 +4,9 @@ require_relative 'spec_helper'
 
 ENV['RAILS_ENV'] = 'test'
 
+require 'simplecov'
+SimpleCov.start 'rails'
+
 require File.expand_path('dummy/config/environment.rb', __dir__)
 
 abort('The Rails environment is running in production mode!') if Rails.env.production?