Doodled a fizzbuzz just because.

fizz.rb

# frozen_string_literal: true

require 'rspec/autorun'

# The rules of FizzBuzz are to count up, replacing numbers divisible by 3 with "Fizz,"
#                                                  numbers divisible by 5 with "Buzz," and
#                                                  numbers divisible by both 3 and 5 with "FizzBuzz";
#                                       otherwise, say the number itself.

class FizzBuzz # :nodoc:
  def self.play(num)
    by_three = (num % 3).zero?
    by_five = (num % 5).zero?
    return 'FizzBuzz' if by_three && by_five
    return 'Fizz' if by_three
    return 'Buzz' if by_five

    num.to_s
  end
end

RSpec.describe 'FizzBuzz Game rules by example' do
  subject(:game) { FizzBuzz }

  it 'one is not divisible by 3' do
    expect(game.play(1)).to eq 1.to_s
  end

  it 'two is not divisible by 3' do
    expect(game.play(2)).to eq 2.to_s
  end

  it 'three is divisible by 3' do
    expect(game.play(3)).to eq 'Fizz'
  end

  it 'four is not divisible by 3' do
    expect(game.play(4)).to eq 4.to_s
  end

  context 'five is not divisible by 3' do
    it 'five is divisible by 5 though' do
      expect(game.play(5)).to eq 'Buzz'
    end
  end

  it 'six is divisible by 3' do
    expect(game.play(6)).to eq 'Fizz'
  end

  it 'seven is not divisible by 3' do
    expect(game.play(7)).to eq 7.to_s
  end

  context 'we have to discuss 15' do
    it '15 is divisible by 5 though too' do
      expect(game.play(15)).to eq 'FizzBuzz'
    end
  end

  it 'nor is 41 divisible by 3' do
    expect(game.play(41)).to eq 41.to_s
  end

  it '42 is divisible by 3' do
    expect(game.play(42)).to eq 'Fizz'
  end

  it '43 and 44 are not divisible by 3' do
    expect(game.play(43)).to eq 43.to_s
    expect(game.play(44)).to eq 44.to_s
  end

  context 'we have to discuss 45' do
    it '45 is divisible by 5 though too' do
      expect(game.play(45)).to eq 'FizzBuzz'
    end
  end

  context 'we have to discuss 55' do
    it '55 is not divisible by 3 though too' do
      expect(game.play(55)).to eq 'Buzz'
    end
  end
end

__END__

FizzBuzz Game rules by example
  one is not divisible by 3
  two is not divisible by 3
  three is divisible by 3
  four is not divisible by 3
  six is divisible by 3
  seven is not divisible by 3
  nor is 41 divisible by 3
  42 is divisible by 3
  43 and 44 are not divisible by 3
  five is not divisible by 3
    five is divisible by 5 though
  we have to discuss 15
    15 is divisible by 5 though too
  we have to discuss 45
    45 is divisible by 5 though too
  we have to discuss 55
    55 is not divisible by 3 though too

Finished in 0.0025 seconds (files took 0.0707 seconds to load)
13 examples, 0 failures