image.rb

class Image

  def initialize(array)
    @array = array
  end

  def output_image
    @array.each { |a| puts a.join }
  end

end

image_spec.rb

require 'rspec'
require 'pry'
require_relative 'image'

RSpec.describe Image do
  it 'returns an image instance' do
    expect(Image.new([])).to be_kind_of Image
  end

  let(:expected_output) { "0000\n0100\n0001\n0000\n" }
  it 'outputs the image in console' do
    array = [
      [0, 0, 0, 0],
      [0, 1, 0, 0],
      [0, 0, 0, 1],
      [0, 0, 0, 0]]
    image = Image.new(array)
    expect { image.output_image }.to output(expected_output).to_stdout
  end
end