diff --git a/tests/factories.py b/tests/factories.py
index b4f9c73..a46e685 100644
--- a/tests/factories.py
+++ b/tests/factories.py
@@ -1,4 +1,6 @@
+from collections.abc import Callable
 from decimal import Decimal
+from typing import Any
 
 from faker import Faker
 from polyfactory.factories.pydantic_factory import ModelFactory
@@ -10,6 +12,12 @@ from src.models.comdirect import ComdirectCreditCard, ComdirectDepot, ComdirectG
 DEFAULT_CATEGORY = "root_category:parent_category:leaf_category"
 
 
+def _faker_or_none(faker: Faker, non_default: Any, default: Any = None, p_value=0.5):
+    if faker.pyfloat(min_value=0.0, max_value=1.0) < p_value:
+        return default
+    return non_default
+
+
 def _amount() -> Decimal:
     return B4wExportFactory.__faker__.pydecimal(
         left_digits=6,
@@ -34,11 +42,9 @@ def _iban() -> str:
     return B4wExportFactory.__faker__.iban()
 
 
-def _other_iban() -> str:
+def _iban_or_none() -> str:
     faker = B4wExportFactory.__faker__
-    if faker.pyint(min_value=0, max_value=100) < 50:
-        return ""
-    return faker.iban()
+    return _faker_or_none(faker, faker.iban(), default="")
 
 
 class B4wExportFactory(ModelFactory[B4wExport]):
@@ -50,7 +56,7 @@ class B4wExportFactory(ModelFactory[B4wExport]):
     Notes = Use(_sentence)
     RmtdNm = Use(_names)
     OwnrAcctIBAN = Use(_iban)
-    RmtdAcctIBAN = Use(_other_iban)
+    RmtdAcctIBAN = Use(_iban_or_none)
 
 
 class ComdirectGiroFactory(ModelFactory[ComdirectGiro]):