chore: import upstream snapshot with attribution

showcase/bin/spec/all_tests.rb

@@ -0,0 +1,12 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+# Entry point for bin/railway minitest suite. Discovers and runs every test_*.rb
+# in this directory.
+
+$LOAD_PATH.unshift(File.expand_path("..", __dir__))
+$LOAD_PATH.unshift(__dir__)
+
+require "minitest/autorun"
+
+Dir.glob(File.join(__dir__, "test_*.rb")).sort.each { |f| require f }