RSpec demo

code.rb

a = gets.to_i
b,c = gets.chomp.split(" ").map(&:to_i)
s = gets.chomp

print("#{a + b + c} #{s}\n")

code_spec.rb

require "open3"

describe 'code test' do
  [
    ["1\n1 2\na\n", "4 1"],
    ["3\n1 2\na\n", "6 1"],
  ].each do |input, expected|
    it("should return #{expected} for input #{input}") do
      Open3.capture3('ruby ./src/code.rb') do |i, o, e, w|
        i.write input
        i.close
        expect(o).to eq expected
      end
    end
  end
end

code_spec_run_on_container.rb

require "open3"

def run_on_container(target, ruby_version: 'latest')
  image = "ruby:#{ruby_version}"
  opts = ['-a', '-v', 'src:/src:ro', '--rm']
  Open3.capture3("docker run #{opts.join(' ')} #{image} /src/#{target}")
end

describe 'code test' do
  [
    ["1\n1 2\na\n", "4 1"],
    ["3\n1 2\na\n", "6 1"],
  ].each do |input, expected|
    it("should return #{expected} for input #{input}") do
      run_on_container('code.rb') do |i, o, e, w|
        i.write input
        i.close
        expect(o).to eq expected
      end
    end
  end
end