ruby rspec capture I/O stdout/stderr

capture_io_spec.rb

require 'pp'

module Helper
  def capture(&block)
    begin
      $stdout = StringIO.new
      $stderr = StringIO.new
      yield
      result = {}
      result[:stdout] = $stdout.string
      result[:stderr] = $stderr.string
    ensure
      $stdout = STDOUT
      $stderr = STDERR
    end
    result
  end
end

RSpec.configure do |config|
  config.include Helper
end



class MyDummy
  def self.do_something
    puts 'hello test'
    $stderr.puts 'error error error'
  end
end

describe MyDummy do
  it "has the correct output" do
    result = capture{ MyDummy.do_something }
    puts "Result:"
    pp result
    puts "###"

    expect(result[:stdout]).to include("hello")
  end
end

RSpec stops (without fails) when sub-command returns status 1 (and stderr).