outlay.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'rails', github: 'rails/rails'
  gem 'arel', github: 'rails/arel'
  gem 'rack', github: 'rack/rack'
  gem 'sprockets', github: 'rails/sprockets'
  gem 'sprockets-rails', github: 'rails/sprockets-rails'
  gem 'sass-rails', github: 'rails/sass-rails'
  gem 'sqlite3'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :outlays, force: true  do |t|
    t.integer :amount
    t.date :date
  end
end

class Outlay < ActiveRecord::Base
end

class BugTest < Minitest::Test
  def test_association_stuff
    Outlay.create!(amount: 20, date: Date.new(2015, 11, 8))
    Outlay.create!(amount: 26, date: Date.new(2015, 11, 7))
    Outlay.create!(amount: 23, date: Date.new(2015, 12, 2))
    Outlay.create!(amount: 3, date: Date.new(2015, 12, 3))

    result = Outlay.select('strftime("%Y-%m-01", date) AS month', 'SUM(amount) AS as_sum').group('month')

    assert_equal 2, result.to_a.size
    assert_equal Date.new(2015, 11, 1), Date.parse(result[0].month)
    assert_equal 46, result[0].as_sum
    assert_equal Date.new(2015, 12, 1), Date.parse(result[1].month)
    assert_equal 26, result[1].as_sum
  end
end