file.rb

class PigLatin
  def initialize
  end

  def convert(original_string)
    word_collection = original_string.split(" ").map(&:downcase)

    word_collection.map! do |word|
      word.match(/(.)(.+)/)
      $2 + $1 + "ay"
    end
    
    word_collection.join(" ")
  end
end

something_spec.rb

require './pig_latin'

describe PigLatin do
  let(:pl) { PigLatin.new }
  describe "#converter" do
    it "accepts an argument" do
      expect{pl.convert("Hello, World")}.not_to raise_error
    end
    
    it "returns the correct output" do
      expect(pl.convert("Hello World")).to eq("ellohay orldway")
    end
  end 
end

p = Piglatin.new
p.convert("a")

Boom!