Adds DB constraint to avoid duplicate balloted investments

db/migrate/20170503163330_add_uniq_index_for_ballot_lines.rb

@@ -0,0 +1,5 @@
+class AddUniqIndexForBallotLines < ActiveRecord::Migration
+  def change
+    add_index :budget_ballot_lines, [:ballot_id, :investment_id], unique: true
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170428111355) do
+ActiveRecord::Schema.define(version: 20170503163330) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -88,6 +88,7 @@ ActiveRecord::Schema.define(version: 20170428111355) do
     t.integer  "heading_id"
   end
 
+  add_index "budget_ballot_lines", ["ballot_id", "investment_id"], name: "index_budget_ballot_lines_on_ballot_id_and_investment_id", unique: true, using: :btree
   add_index "budget_ballot_lines", ["ballot_id"], name: "index_budget_ballot_lines_on_ballot_id", using: :btree
   add_index "budget_ballot_lines", ["investment_id"], name: "index_budget_ballot_lines_on_investment_id", using: :btree
 

spec/models/budget/ballot_spec.rb

@@ -2,6 +2,29 @@ require 'rails_helper'
 
 describe Budget::Ballot do
 
+  describe "validations" do
+
+    it "should be valid" do
+      budget = create(:budget)
+      ballot = create(:budget_ballot, budget: budget)
+
+      expect(ballot).to be_valid
+    end
+
+    it "should not be valid with the same investment twice" do
+      budget = create(:budget)
+      group  = create(:budget_group, budget: budget)
+      heading = create(:budget_heading, group: group)
+      investment = create(:budget_investment, :selected, heading: heading)
+
+      ballot = create(:budget_ballot, budget: budget)
+      ballot.investments << investment
+
+      expect { ballot.investments << investment }.to raise_error(ActiveRecord::RecordNotUnique)
+    end
+
+  end
+
   describe "#amount_spent" do
     it "returns the total amount spent in investments" do
       budget = create(:budget)