adds ballot model spec

spec/models/budget/ballot_spec.rb

@@ -0,0 +1,43 @@
+require 'rails_helper'
+
+describe Budget::Ballot do
+
+  describe "#amount_spent" do
+    it "returns the total amount spent in investments" do
+      inv1 = create(:budget_investment, :feasible, price: 10000)
+      inv2 = create(:budget_investment, :feasible, price: 20000)
+
+      ballot = create(:budget_ballot)
+      ballot.investments << inv1
+
+      expect(ballot.total_amount_spent).to eq 10000
+
+      ballot.investments << inv2
+
+      expect(ballot.total_amount_spent).to eq 30000
+    end
+  end
+
+  describe "#amount_spent by heading" do
+    it "returns the amount spent on all investments assigned to a specific heading" do
+      heading = create(:budget_heading)
+      inv1 = create(:budget_investment, :feasible, price: 10000, heading: heading)
+      inv2 = create(:budget_investment, :feasible, price: 20000, heading: create(:budget_heading))
+      inv3 = create(:budget_investment, :feasible, price: 25000)
+      inv4 = create(:budget_investment, :feasible, price: 40000, heading: heading)
+
+      ballot = create(:budget_ballot)
+      ballot.investments << inv1
+      ballot.investments << inv2
+      ballot.investments << inv3
+
+      expect(ballot.amount_spent(heading.id)).to eq 10000
+      expect(ballot.amount_spent(nil)).to eq 25000
+
+      ballot.investments << inv4
+
+      expect(ballot.amount_spent(heading.id)).to eq 50000
+    end
+  end
+
+end