Kata Prime Factors

prime-factors.rb

require 'minitest/autorun'

def primes(input)
  out, curr_div = [], 2
  begin
    div, mod = input.divmod(curr_div)
    if mod.zero?
      out << curr_div
      input = div
    else
      curr_div += 1
    end
    raise if input >= curr_div
  rescue => e
    retry
  end
  out
end

describe 'PrimeFactors' do

  describe "Compute the prime factors" do
    it "must to return the primes of a given natural number" do
      primes(1).must_equal   []
      primes(2).must_equal   [2]
      primes(3).must_equal   [3]
      primes(4).must_equal   [2,2]
      primes(5).must_equal   [5]
      primes(6).must_equal   [2,3]
      primes(7).must_equal   [7]
      primes(8).must_equal   [2,2,2]
      primes(9).must_equal   [3,3]
      primes(12).must_equal  [2,2,3]
      primes(126).must_equal [2,3,3,7]
    end
  end

end