[#6574] Add a TimeEntryActivity to OverheadBudgets

test/unit/overhead_budget_test.rb

@@ -2,6 +2,9 @@ require File.dirname(__FILE__) + '/../test_helper'
 
 class OverheadBudgetTest < ActiveSupport::TestCase
   should_belong_to :deliverable
+  should_belong_to :time_entry_activity
+
+  should_validate_presence_of :time_entry_activity_id
 
   context "#budget=" do
     should "strip dollar signs when writing" do