fizz_buzz_spec.rb

class FizzBuzz
  def self.say(num)
    str = [[:Fizz][num%3], [:Buzz][num%5]].join('')
    str.empty? ? num : str
  end
end

describe FizzBuzz do
  subject { described_class.say(num) }
  context 'with 1' do
    let(:num) { 1 }
    it { should eq 1 }
  end

  context 'with 3' do
    let(:num) { 3 }
    it { should eq 'Fizz' }
  end

  context 'with 5' do
    let(:num) { 5 }
    it { should eq 'Buzz' }
  end

  context 'with 15' do
    let(:num) { 15 }
    it { should eq 'FizzBuzz' }
  end
end