Use updatable slug factory trait to sluggable concern

Slugs should only be updated on certain conditions, we need a trait that
meets that conditions and the name of the trait passed as a mandatory &
named argument on the sluggable concern

spec/models/budget/group_spec.rb

@@ -4,7 +4,7 @@ describe Budget::Group do
 
   let(:budget) { create(:budget) }
 
-  it_behaves_like "sluggable"
+  it_behaves_like "sluggable", updatable_slug_trait: :drafting_budget
 
   describe "name" do
     before do

spec/models/budget/heading_spec.rb

@@ -5,7 +5,7 @@ describe Budget::Heading do
   let(:budget) { create(:budget) }
   let(:group) { create(:budget_group, budget: budget) }
 
-  it_behaves_like "sluggable"
+  it_behaves_like "sluggable", updatable_slug_trait: :drafting_budget
 
   describe "name" do
     before do

spec/models/budget_spec.rb

@@ -4,7 +4,7 @@ describe Budget do
 
   let(:budget) { create(:budget) }
 
-  it_behaves_like "sluggable"
+  it_behaves_like "sluggable", updatable_slug_trait: :drafting
 
   describe "name" do
     before do

spec/models/concerns/sluggable.rb

@@ -1,6 +1,6 @@
 require 'spec_helper'
 
-shared_examples_for 'sluggable' do
+shared_examples_for 'sluggable' do |updatable_slug_trait:|
 
   describe 'generate_slug' do
     let(:factory_name) { described_class.name.parameterize('_').to_sym }
@@ -11,5 +11,20 @@ shared_examples_for 'sluggable' do
         expect(sluggable.slug).to eq("marlo-branido-carlo")
       end
     end
+
+    context "slug updating condition is true" do
+      it "slug is updated" do
+        updatable = create(factory_name, updatable_slug_trait, name: 'Old Name')
+        expect{updatable.update_attributes(name: 'New Name')}
+          .to change{ updatable.slug }.from('old-name').to('new-name')
+      end
+    end
+
+    context "slug updating condition is false" do
+      it "slug isn't updated" do
+        expect{sluggable.update_attributes(name: 'New Name')}
+          .not_to (change{ sluggable.slug })
+      end
+    end
   end
 end