Changes suggested in the PR made

app/controllers/admin/budget_headings_controller.rb

@@ -3,30 +3,30 @@ class Admin::BudgetHeadingsController < Admin::BaseController
   feature_flag :budgets
 
   def create
-    @budget = Budget.find params[:budget_id]
-    @budget_group = @budget.groups.find params[:budget_group_id]
+    @budget = Budget.find(params[:budget_id])
+    @budget_group = @budget.groups.find(params[:budget_group_id])
     @budget_group.headings.create(budget_heading_params)
     @headings = @budget_group.headings
   end
 
   def edit
-    @budget = Budget.find params[:budget_id]
-    @budget_group = @budget.groups.find params[:budget_group_id]
-    @heading = Budget::Heading.find params[:id]
+    @budget = Budget.find(params[:budget_id])
+    @budget_group = @budget.groups.find(params[:budget_group_id])
+    @heading = Budget::Heading.find(params[:id])
   end
 
   def update
-    @budget = Budget.find params[:budget_id]
-    @budget_group = @budget.groups.find params[:budget_group_id]
-    @heading = Budget::Heading.find params[:id]
+    @budget = Budget.find(params[:budget_id])
+    @budget_group = @budget.groups.find(params[:budget_group_id])
+    @heading = Budget::Heading.find(params[:id])
     @heading.assign_attributes(budget_heading_params)
-    @errors = @heading.errors.full_messages unless @heading.save
+    render :edit unless @heading.save
   end
 
   def destroy
-    @heading = Budget::Heading.find params[:id]
+    @heading = Budget::Heading.find(params[:id])
     @heading.destroy
-    @budget = Budget.find params[:budget_id]
+    @budget = Budget.find(params[:budget_id])
     redirect_to admin_budget_path(@budget)
   end
 

app/views/admin/budget_headings/update.js.erb

@@ -1,5 +1 @@
-<% if @errors %>
-  $("#heading-<%=@heading.id%> div#error_explanation").replaceWith("<%= j render("admin/budget_headings/errors", errors: @errors) %>");
-<% else %>
-  $("#heading-<%=@heading.id%>").html("<td colspan='4'><%= j render("admin/budgets/heading", group: @budget_group, budget: @budget, heading: @heading) %></td>");
-<%  end %>
+$("#<%= dom_id(@budget_group) %>").html('<%= j render("admin/budgets/group", group: @budget_group, headings: @budget_group.headings) %>');

app/views/admin/budgets/_heading_form.html.erb

@@ -1,4 +1,5 @@
 <%= form_for [:admin, budget, group, heading], remote: true do |f| %>
+  <%= render 'shared/errors', resource: heading %>
   <label><%= t("admin.budgets.form.heading") %></label>
   <%= f.text_field :name,
                     label: false,
@@ -25,6 +26,4 @@
   </div>
 
   <%= f.submit t("admin.budgets.form.save_heading"), class: "button success" %>
-  
-  <div id="error_explanation"></div>
 <% end %>

spec/models/budget/heading_spec.rb

@@ -26,7 +26,7 @@ describe Budget::Heading do
   end
 
   describe "heading" do
-    it "can be deleted if not budget's investments associated" do
+    it "can be deleted if no budget's investments associated" do
       heading1 = create(:budget_heading, group: group, name: 'name')
       heading2 = create(:budget_heading, group: group, name: 'name 2')
 
@@ -34,7 +34,6 @@ describe Budget::Heading do
 
       expect(heading1.can_be_deleted?).to eq false
       expect(heading2.can_be_deleted?).to eq true
-
     end
   end