add tests for the Ruby backend

main-server/Gemfile

@@ -1,7 +1,13 @@
 source "https://rubygems.org"
 
 gem "rails", "~> 8.1.2"
+# Use sqlite3 as the database for Active Record in development/test
 gem "sqlite3", ">= 2.1"
+
+# Use PostgreSQL in production
+group :production do
+  gem "pg", "~> 1.5"
+end
 gem "puma", ">= 5.0"
 
 # Use Active Model has_secure_password [https://guides.rubyonrails.org/active_model_basics.html#securepassword]
@@ -34,9 +40,14 @@ gem "rack-cors"
 
 group :development, :test do
   gem "debug", platforms: %i[ mri windows ], require: "debug/prelude"
+  gem "rspec-rails", "~> 8.0"
   gem "bundler-audit", require: false
   gem "brakeman", require: false
   gem "rubocop-rails-omakase", require: false
 end
 
 gem "redis", "~> 6.0"
+
+group :test do
+  gem "simplecov", require: false
+end