Faking the console in Ruby

A few days ago, I was preparing an assignment for a job process both in Java and in Ruby. While doing in Java, I decided to test the engine. But in Ruby I wanted to test the whole application, including the communication via standard input/output on the console.

And how do you mock standard input/output in Ruby?. Well. It turns out it is quite easy to do it with Rspec. But I wanted to do it without any additional requirement. How do you mock STDIN and STDOUT in plain Ruby.

It turns out it isn’t difficult. Based on this gist, I prepared my own solution. First the input faker:

class InputFaker

  def feedStrings(strings)

    @strings = strings

  end

  def gets

    next_string = @strings.shift

    next_string #TODO: I guess next_string is superflous

  end

end

class OutputFaker

  def initialize

    @result=[]

  end

  def write(str)

    @result << str.chomp

  end

  def clear

    @result=[]

  end

  def result

    @result.join 

  end

end

  def setup

    $stdin = InputFaker.new

    $stdout = OutputFaker.new

    @robotUI=RobotUI.new unless @robotUI

  end

  def teardown

    $stdin = STDIN

    $stdout = STDOUT 

  end

  def actual_test(array_of_inputs,expected_output)

   $stdin.feedStrings(array_of_inputs)

    array_of_inputs.size.times{@robotUI.parse()}

    assert_equal(expected_output,$stdout.result)

  end