Add test for global mass assignment disable

for Rails 2

test/tests/test_mass_assign_disable.rb

+class MassAssignDisableTest < Test::Unit::TestCase
+  include BrakemanTester::RescanTestHelper
+
+  def mass_assign_disable content
+    init = "config/initializers/mass_assign.rb"
+
+    before_rescan_of init, "rails2" do
+      write_file init, content
+    end
+
+    assert_changes
+    assert_fixed 3
+    assert_new 0
+  end
+
+  def test_disable_mass_assignment_by_send
+    mass_assign_disable "ActiveRecord::Base.send(:attr_accessible, nil)"
+  end
+
+  def test_disable_mass_assignment_by_module
+    mass_assign_disable <<-RUBY
+      module ActiveRecord
+        class Base
+          attr_accessible
+        end
+      end
+    RUBY
+  end
+
+  def test_disable_mass_assignment_by_module_and_nil
+    mass_assign_disable <<-RUBY
+      module ActiveRecord
+        class Base
+          attr_accessible nil
+        end
+      end
+    RUBY
+  end
+end