Add autobind fix if invoice with this sum is already present

app/models/bank_transaction.rb

@@ -17,7 +17,7 @@ class BankTransaction < ApplicationRecord
   end
 
   def invoice
-    @invoice ||= registrar.invoices.find_by(total: sum) if registrar
+    @invoice ||= registrar.invoices.order(created_at: :asc).unpaid.find_by(total: sum) if registrar
   end
 
   def registrar

test/models/bank_transaction_test.rb

@@ -15,6 +15,57 @@ class BankTransactionTest < ActiveSupport::TestCase
     end
   end
 
+  def test_binds_if_this_sum_invoice_already_present
+    create_payable_invoice(number: '2222', total: 10, reference_no: '1234567')
+    another_invoice = @invoice.dup
+    another_invoice.save(validate: false)
+    another_invoice.update(reference_no: '7654321', number: '2221')
+
+    another_item = @invoice.items.first.dup
+    another_item.invoice = another_invoice
+    another_item.save
+    another_invoice.reload
+
+    first_transaction = BankTransaction.new(description: 'invoice #2221',
+                                            sum: 10,
+                                            description: 'Order nr 1 from registrar 1234567 second number 2345678')
+
+    first_transaction.create_activity(another_invoice.buyer, another_invoice)
+
+    transaction = BankTransaction.new(description: 'invoice #2222',
+                                      sum: 10,
+                                      description: 'Order nr 1 from registrar 1234567 second number 2345678')
+
+    assert_difference 'AccountActivity.count' do
+      transaction.autobind_invoice
+    end
+  end
+
+  def test_marks_the_first_one_as_paid_if_same_sum
+    create_payable_invoice(number: '2222', total: 10, reference_no: '1234567')
+    another_invoice = @invoice.dup
+    another_invoice.save(validate: false)
+    another_invoice.update(reference_no: '7654321', number: '2221')
+
+    another_item = @invoice.items.first.dup
+    another_item.invoice = another_invoice
+    another_item.save
+    another_invoice.reload
+
+    transaction = BankTransaction.new(description: 'invoice #2222',
+                                      sum: 10,
+                                      description: 'Order nr 1 from registrar 1234567 second number 2345678')
+
+    assert_difference 'AccountActivity.count' do
+      transaction.autobind_invoice
+    end
+
+    @invoice.reload
+    another_invoice.reload
+    assert(@invoice.paid?)
+    assert_not(another_invoice.paid?)
+  end
+
   def test_matches_against_invoice_nubmber_and_reference_number_in_description
     create_payable_invoice(number: '2222', total: 10, reference_no: '1234567')
     transaction = BankTransaction.new(description: 'invoice #2222',