gistfile1.rb

# Original from Mitchell

  def self.first_uninteresting
    all_numbers = Number.find(:all).map { |entry| entry.number }.sort
    last = 0
    all_numbers.each do |number|
      if number != last + 1
        return last + 1
      end
      last = number
    end
    return last + 1
  end


#-----------------------------------------------------------------------------------------
#NEW

class Interesting < ActiveRecord::Base
  def self.lowest_number
    previous = -1
    all(:order=>:number, :conditions=>"number >= 0").each do |number|
      break if previous != number.number - 1
      previous = number.number
    end
    previous + 1
  end
end

#==================
#Tests

require 'test_helper'
class InterestingTest < ActiveSupport::TestCase
  def setup
    Interesting.destroy_all
  end

  def test_should_return_lowest_number
    [0, 1, 2, 3, 4, 6, 100].each {|value| Interesting.create(:number=>value)}
    assert_equal 5, Interesting.lowest_number
  end

  def test_should_return_lowest_number_when_starts_at_1
    [1,2,4].each {|value| Interesting.create(:number=>value)}
    assert_equal 0, Interesting.lowest_number
  end

  def test_should_return_lowest_number_when_only_0_entry
    [0].each {|value| Interesting.create(:number=>value)}
    assert_equal 1, Interesting.lowest_number
  end

  def test_should_return_lowest_number_when_db_empty
    assert_equal 0, Interesting.lowest_number
  end
  
  def test_should_return_lowest_number_and_ignore_negatives
    [-10, -5, -3].each {|value| Interesting.create(:number=>value)}
    assert_equal 0, Interesting.lowest_number
  end

  def test_should_return_lowest_number_and_ignore_negatives_and_still_return_next_positive_number
    [-10, -5, -3, 0, 1, 2, 10].each {|value| Interesting.create(:number=>value)}
    assert_equal 3, Interesting.lowest_number
  end
end