gistfile1.txt

require 'spec_helper'

describe Bid do
  before(:each) do
    @user = Factory(:user)
    @user.funds = 10
    @user.save()
    @prediction = Factory(:prediction)
    @attr=  {
      :user_id => @user.id,
      :prediction_id => @prediction.id,
      :txn => 10,
      :bet => true
    }
  end

  it "should create a new instance given valid attributes" do
    @user.bids.create(@attr)
    @user.save()
    @user.bids.size.should == 1
    @user.funds.should == 0
  end

  it "should not create a new instance if funds is below txn" do
    @user.funds = 9
    @user.save()
    @user.bids.create(@attr)
    @user.save()
    @user.bids.size.should == 0
    @user.funds.should == 1
  end

  it "should not create a new instance if prediction id is empty" do
    @user.bids.create(@attr.merge(:prediction_id => nil))
    @user.save()
    @user.bids.size.should == 0
  end
end

gistfile2.txt

class Bid < ActiveRecord::Base
  belongs_to :user
  validate :check_fund
  validates_presence_of :prediction_id
  def check_fund
    errors.add(:user, "'s funds is insufficent") unless user.funds >= self.txn
  end
end