Update setup script for removed callbacks

We removed some Spree magic a while back and that broke our sample data
script. This is now corrected.

I also added a spec so that we will notice broken seed data earlier.

lib/tasks/sample_data/order_factory.rb

@@ -31,6 +31,7 @@ module SampleData
 
       log "- complete order - shipped"
       order = create_complete_order
+      order.payments.first.amount = order.total
       order.payments.first.capture!
       order.save
       order.shipment.reload.ship!

spec/lib/tasks/sample_data_rake_spec.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rake'
+
+describe 'sample_data.rake' do
+  before(:all) do
+    Rake.application.rake_require 'tasks/sample_data'
+    Rake::Task.define_task(:environment)
+  end
+
+  before do
+    # Create seed data required by the sample data.
+    create(:user)
+    DefaultStockLocation.find_or_create
+    DefaultShippingCategory.find_or_create
+  end
+
+  it "creates some sample data to play with" do
+    Rake.application.invoke_task "ofn:sample_data"
+
+    expect(EnterpriseGroup.count).to eq 1
+    expect(Customer.count).to eq 2
+    expect(Spree::Order.count).to eq 5
+  end
+end