Put tests in their own directory and add rake task to run them

README.md

@@ -4,12 +4,13 @@
 
 * Ruby 4.0.6
 * Minitest 6.0.6
+* Rake 13.4.2
 
 ## Instructions
 
 Checkout class is in `checkout.rb`
 
-Run tests with `ruby -Ilib:test tests.rb`
+Run tests with `rake test`
 
 `main.rb` is a scratchpad
 

Rakefile

@@ -0,0 +1,3 @@
+require "minitest/test_task"
+
+Minitest::TestTask.create

test/checkout_test.rb

@@ -1,8 +1,8 @@
 require "minitest/autorun"
 
-require "./checkout.rb"
+require "checkout.rb"
 
-class TestCheckout < Minitest::Test
+class CheckoutTest < Minitest::Test
   def setup
     @checkout = Checkout.new
   end