Kata Fizz Buzz

fizzbuzz.rb

require 'minitest/autorun'

class FizzBuzz
  class FizzBuzz::NonNatural < StandardError; end

  def self.check(input)
    raise NonNatural if !input.is_a?(Integer) || input < 1

    if input % 15 == 0
      'fizzbuzz'
    elsif input % 3 == 0
      'fizz'
    elsif input % 5 == 0
      'buzz'
    else
      input
    end
  end
end

describe FizzBuzz do

  describe "non divisible" do
    it "must to return the same input" do
      FizzBuzz.check(1).must_equal 1
      FizzBuzz.check(2).must_equal 2
      FizzBuzz.check(4).must_equal 4
    end

    it "must to raise a FizzBuzz::NonNatural execption when the input is not a natural number" do
      proc { 
        FizzBuzz.check(-1)
      }.must_raise FizzBuzz::NonNatural
      
      proc { 
        FizzBuzz.check(1.5)
      }.must_raise FizzBuzz::NonNatural
      
      proc { 
        FizzBuzz.check('1.5')
      }.must_raise FizzBuzz::NonNatural
    end
  end

  describe "fizz" do
    it "must to return 'fizz' when the input is dividable by 3" do
      FizzBuzz.check(3).must_equal "fizz"
      FizzBuzz.check(6).must_equal "fizz"
    end
  end

  describe "buzz" do
    it "must to return 'buzz' when the input is dividable by 5" do
      FizzBuzz.check(5).must_equal "buzz"
      FizzBuzz.check(10).must_equal "buzz"
    end
  end

  describe "fizzbuzz" do
    it "must to return 'fizzbuzz' when the input is dividable by 15" do
      FizzBuzz.check(15).must_equal "fizzbuzz"
    end
  end

end