Sample implementation for count_by_word. Please see: http://qiita.com/jnchito/items/c4a56046be1096c19b1c

count_by_word_spec.rb

def count_by_word(string)
  string
    .scan(/\w+/)
    .group_by{|s| s}
    .map{|word, words| [word, words.size]}
    .to_h # require Ruby 2.1 or higher
end

describe "count by word" do
  it "counts by word" do
    expect(count_by_word("no ruby no life")).to eq("no" => 2, "life" => 1, "ruby" => 1)
  end
end