Improve tests

- Remove unnecessary fixtures
- Remove unnecessary teardown steps
- Improve readability

test/models/payment_orders/every_pay_test.rb

@@ -4,11 +4,8 @@ class EveryPayTest < ActiveSupport::TestCase
   def setup
     super
 
-    @invoice = invoices(:for_payments_test)
-    invoice_item = invoice_items(:one)
-
-    @invoice.items << invoice_item
-    @invoice.items << invoice_item
+    @invoice = invoices(:one)
+    @invoice.update!(total: 12)
 
     params = {
       response:
@@ -41,12 +38,6 @@ class EveryPayTest < ActiveSupport::TestCase
     travel_to Time.zone.parse('2018-04-01 00:30:00 +0000')
   end
 
-  def teardown
-    super
-
-    travel_back
-  end
-
   def test_form_fields
     expected_fields = {
       api_username: 'api_user',