add specs

app/models/concerns/invoice_common.rb

@@ -0,0 +1,34 @@
+# app/models/concerns/invoice_common.rb
+module InvoiceCommon
+    extend ActiveSupport::Concern
+  
+    included do
+      include InvoiceHelper
+  
+      validates_presence_of :invoice_number
+      validates_uniqueness_of :invoice_number
+      validate :tax_number_set
+  
+      after_initialize :init, unless: :persisted?
+    end
+  
+    def mark_sepa_downloaded
+      self.sepa_downloaded = true
+      save
+    end
+  
+    def unmark_sepa_downloaded
+      self.sepa_downloaded = false
+      save
+    end
+  
+    def name
+      I18n.t("activerecord.attributes.#{self.class.name.underscore}.name") + "_#{invoice_number}"
+    end
+  
+    def tax_number_set
+      return if FoodsoftConfig[:contact][:tax_number].present?
+      errors.add(:base, "Keine Steuernummer in FoodsoftConfig :contact gesetzt")
+    end
+  end
+