Add additional model and integration tests

This commit adds new tests for a better coverage.

integration/
  * home
  * supplier

models/
  * article
  * delivery
  * group_order_article
  * supplier

also adds a new factory for delivery

Co-authored-by: viehlieb <pf@pragma-shift.net>
Co-authored-by: Tobias Kneuker <tk@pragma-shift.net>

spec/models/delivery_spec.rb

@@ -0,0 +1,23 @@
+require_relative '../spec_helper'
+
+describe Delivery do
+  let(:delivery) { create :delivery }
+  let(:stock_article) { create :stock_article, price: 3 }
+
+  it 'creates new stock_changes' do
+    delivery.new_stock_changes = ([
+      {
+        quantity: 1,
+        stock_article: stock_article
+      },
+      {
+        quantity: 2,
+        stock_article: stock_article
+      }
+    ])
+
+    expect(delivery.stock_changes.last[:stock_article_id]).to be stock_article.id
+    expect(delivery.includes_article?(stock_article)).to be true
+    expect(delivery.sum(:net)).to eq 9
+  end
+end