diff --git a/erpnext/accounts/doctype/payment_entry/test_payment_entry.py b/erpnext/accounts/doctype/payment_entry/test_payment_entry.py
index edfec41..b3511f0 100644
--- a/erpnext/accounts/doctype/payment_entry/test_payment_entry.py
+++ b/erpnext/accounts/doctype/payment_entry/test_payment_entry.py
@@ -6,10 +6,11 @@
 import frappe
 from frappe import qb
 from frappe.tests.utils import FrappeTestCase, change_settings
-from frappe.utils import flt, nowdate
+from frappe.utils import add_days, flt, nowdate
 
 from erpnext.accounts.doctype.payment_entry.payment_entry import (
 	InvalidPaymentEntry,
+	get_outstanding_reference_documents,
 	get_payment_entry,
 	get_reference_details,
 )
@@ -1262,6 +1263,42 @@
 		so.reload()
 		self.assertEqual(so.advance_paid, so.rounded_total)
 
+	def test_outstanding_invoices_api(self):
+		"""
+		Test if `get_outstanding_reference_documents` fetches invoices in the right order.
+		"""
+		customer = create_customer("Max Mustermann", "INR")
+		create_payment_terms_template()
+
+		si = create_sales_invoice(qty=1, rate=100, customer=customer)
+		si2 = create_sales_invoice(do_not_save=1, qty=1, rate=100, customer=customer)
+		si2.payment_terms_template = "Test Receivable Template"
+		si2.submit()
+
+		args = {
+			"posting_date": nowdate(),
+			"company": "_Test Company",
+			"party_type": "Customer",
+			"payment_type": "Pay",
+			"party": customer,
+			"party_account": "Debtors - _TC",
+		}
+		args.update(
+			{
+				"get_outstanding_invoices": True,
+				"from_posting_date": nowdate(),
+				"to_posting_date": add_days(nowdate(), 7),
+			}
+		)
+		references = get_outstanding_reference_documents(args)
+
+		self.assertEqual(len(references), 3)
+		self.assertEqual(references[0].voucher_no, si.name)
+		self.assertEqual(references[1].voucher_no, si2.name)
+		self.assertEqual(references[2].voucher_no, si2.name)
+		self.assertEqual(references[1].payment_term, "Basic Amount Receivable")
+		self.assertEqual(references[2].payment_term, "Tax Receivable")
+
 
 def create_payment_entry(**args):
 	payment_entry = frappe.new_doc("Payment Entry")
@@ -1322,6 +1359,9 @@
 def create_payment_terms_template_with_discount(
 	name=None, discount_type=None, discount=None, template_name=None
 ):
+	"""
+	Create a Payment Terms Template with %  or amount discount.
+	"""
 	create_payment_term(name or "30 Credit Days with 10% Discount")
 	template_name = template_name or "Test Discount Template"