running_man.rb

require 'open3'
class RunningMan
  def initialize(*cmd)
    @cmd = cmd
  end

  attr_reader :status, :output, :error

  def run
    input, output, err = Open3.popen3(*@cmd)
    input.close
    @output = output.read
    @error = err.read
    @status = $?
    output.close
    err.close
    success?
  end

  def exit_status
    status.try(:exitstatus)
  end

  def success?
    status.try(:success?)
  end
end

running_man_spec.rb

equire 'spec_helper'

describe RunningMan do
  describe "initialize" do
    it "takes a command string or a command and list of arguments as its parameter" do
      RunningMan.new("which")
      RunningMan.new("which", "ls")
    end
  end
  
  describe "#run" do    
    subject { RunningMan.new("echo hi") }

    it "executes the command" do
      subject.run
    end
    
    it "returns the process exit status as true on success" do
      subject.stub(:success?).and_return(true)
      subject.run.should be_true
    end
    
    it "returns the process exit status as false on failure" do
      subject.stub(:success?).and_return(false)
      subject.run.should be_false
    end
  end

  describe "#exit_status" do
    before do
      @in, @out, @err = StringIO.new, StringIO.new, StringIO.new
      Open3.stub(:popen3).and_return([@in, @out, @err])
      Process.stub(:wait)
    end

    subject { RunningMan.new("asdf") }
    
    it "returns the numerical value of the process status" do
      $?.stub(:exitstatus).and_return(1)
      subject.run
      subject.exit_status.should == 1
    end
  end

  describe "input/output" do
    before do
      @in, @out, @err = StringIO.new, StringIO.new, StringIO.new
      Open3.stub(:popen3).and_return([@in, @out, @err])
      Process.stub(:wait)
    end

    subject { RunningMan.new("asdf") }
    
    it "records the process' STDOUT and makes it accessible" do
      @out << "standard output"
      @out.rewind
      subject.run
      subject.output.should == "standard output"
    end

    it "records the process' STDERR and makes it accessible" do
      @err << "standard error"
      @err.rewind
      subject.run
      subject.error.should == "standard error"
    end
  end
end