netengine_golf.rb

require 'rspec'
require 'json'
require 'active_support/all'
require 'pry'

def input
  [
    {lastmodificationdate:"2012-11-16",userproject:'FCBIZ',totalcost:10},
    {lastmodificationdate:"2012-11-16",userproject:'LMS',totalcost:20},
    {lastmodificationdate:"2012-11-16",userproject:'NetEngine',totalcost:52},
    {lastmodificationdate:"2012-11-17",userproject:'FCBIZ',totalcost:11},
    {lastmodificationdate:"2012-11-17",userproject:'LMS',totalcost:22},
    {lastmodificationdate:"2012-11-17",userproject:'NetEngine',totalcost:53},
    {lastmodificationdate:"2012-11-18",userproject:'FCBIZ',totalcost:34},
    {lastmodificationdate:"2012-11-18",userproject:'LMS',totalcost:32},
    {lastmodificationdate:"2012-11-18",userproject:'NetEngine',totalcost:55}
  ]
end

def desired_output
  [
    { :lastmodificationdate => "2012-11-16", "FCBIZ" => 10, "LMS" => 20, "NetEngine" => 52 },
    { :lastmodificationdate => "2012-11-17", "FCBIZ" => 11, "LMS" => 22, "NetEngine" => 53 },
    { :lastmodificationdate => "2012-11-18", "FCBIZ" => 34, "LMS" => 32, "NetEngine" =>55}
  ]
end

class NetEngineGolf
  def jim(input)
    input.group_by { |a| a[:lastmodificationdate] }.map do |date, values|
      values.inject({ lastmodificationdate: date }) do |hash, value|
        hash.merge value[:userproject] => value[:totalcost]
      end 
    end 
  end 
end

describe NetEngineGolf do
  describe "#jim" do
    it "turns the input into the output" do
      output = NetEngineGolf.new.jim_1(input)
      output.should == desired_output
    end 
  end 
end

Thanks!! Exactly what I needed and in few minutes... impressive!!