fix rounding error caused by item quantity

when applying the line item quantity causes sub-cent amounts, the total needs to be rounded to 2 digits again.

fix #46

Author: langalex

lib/secretariat/invoice.rb

@@ -121,12 +121,12 @@ def valid?
       @errors = []
       tax = BigDecimal(tax_amount)
       basis = BigDecimal(basis_amount)
-      summed_tax_amount = taxes.sum(&:tax_amount)
+      summed_tax_amount = taxes.sum(&:tax_amount).round(2)
       if tax != summed_tax_amount
         @errors << "Tax amount and summed tax amounts deviate: #{tax_amount} / #{summed_tax_amount}"
         return false
       end
-      summed_tax_base_amount = taxes.sum(&:base_amount)
+      summed_tax_base_amount = taxes.sum(&:base_amount).round(2)
       if basis != summed_tax_base_amount
         @errors << "Base amount and summed tax base amount deviate: #{basis} / #{summed_tax_base_amount}"
         return false

test/invoice_test.rb

@@ -791,5 +791,20 @@ def test_invoice_object_extensions
       assert_match(/<ram:PaymentReference>#{invoice.payment_reference}<\/ram:PaymentReference>/, xml)
       assert_match(%r{<ram:DefinedTradeContact>\s*<ram:PersonName>Max Mustermann</ram:PersonName>\s*</ram:DefinedTradeContact>}, xml)
     end
+
+    def test_invoice_with_quantity_causing_sub_cent_amounts
+      invoice = make_de_invoice
+      invoice.tax_calculation_method = :ITEM_BASED
+      invoice.line_items.first.net_amount = BigDecimal('10.12')
+      invoice.line_items.first.billed_quantity = BigDecimal('0.1')
+      invoice.line_items.first.charge_amount = BigDecimal('1.01')
+      invoice.line_items.first.tax_amount = BigDecimal('0.19')
+      invoice.basis_amount = BigDecimal('1.01') # 1.012 rounded
+      invoice.tax_amount = BigDecimal('0.19')
+      invoice.grand_total_amount = BigDecimal('1.2')
+
+      invoice.valid?
+      assert_equal [], invoice.errors
+    end
   end
 end