Prime Factors Kata 4th iteration

prime_factor_decomposer.rb

module PrimeFactorDecomposer 
  def decompose(number)
    return [number] if prime?(number)
    
    primes = [] 
    2.upto(number / 2) do |candidate|
      while (number % candidate).zero? do
        primes << candidate
        number = number / candidate
      end
    end
    primes
  end

  def prime?(number)
    return false if number == 1

    (2..Math.sqrt(number)).each do |i|
      return false if (number %i).zero?
    end
    true
  end
end

prime_factor_decomposer_spec.rb

describe PrimeFactorDecomposer do
  include PrimeFactorDecomposer

  it "returns no prime factors for 1" do
    decompose(1).should be_empty
  end

  it "decomposes 2 into 2" do
    decompose(2).should be == [2]
  end

  it "decomposes 3 into 3" do
    decompose(3).should be == [3]
  end
  
  it "decomposes 4 into 2,2" do
    decompose(4).should be == [2,2]
  end

  it "decomposes 5 into 5" do
    decompose(5).should be == [5]
  end

  it "decomposes 12 into 2,2,3" do
    decompose(12).should be == [2,2,3]
  end
end

spec output

PrimeFactorDecomposer
  returns no prime factors for 1
  decomposes 2 into 2
  decomposes 3 into 3
  decomposes 4 into 2,2
  decomposes 5 into 5
  decomposes 12 into 2,2,3

Finished in 0.00441 seconds
6 examples, 0 failures

I like better how this reads now. The case that Nikolai discovered https://gist.github.com/3045485/1fc71bf3fd39e0943661e5c50769e5829f6a2ccf is fixed now.

It seems the prime? part is needed in order for this to work.

Also i am not sure if the module approach is the best one. The tests read beautiful at least.. I need a few more iterations to know i guess.