fix: flaky demo test case

erpnext/accounts/party.py

@@ -635,9 +635,7 @@ def get_due_date_from_template(template_name, posting_date, bill_date):
 	return due_date
 
 
-def validate_due_date(
-	posting_date, due_date, party_type, party, company=None, bill_date=None, template_name=None
-):
+def validate_due_date(posting_date, due_date, bill_date=None, template_name=None):
 	if getdate(due_date) < getdate(posting_date):
 		frappe.throw(_("Due Date cannot be before Posting / Supplier Invoice Date"))
 	else:

erpnext/controllers/accounts_controller.py

@@ -561,18 +561,12 @@ class AccountsController(TransactionBase):
 			validate_due_date(
 				self.posting_date,
 				self.due_date,
-				"Customer",
-				self.customer,
-				self.company,
 				self.payment_terms_template,
 			)
 		elif self.doctype == "Purchase Invoice":
 			validate_due_date(
 				self.bill_date or self.posting_date,
 				self.due_date,
-				"Supplier",
-				self.supplier,
-				self.company,
 				self.bill_date,
 				self.payment_terms_template,
 			)

erpnext/setup/demo.py

@@ -149,6 +149,11 @@ def convert_order_to_invoices():
 			invoice.set_posting_time = 1
 			invoice.posting_date = order.transaction_date
 			invoice.due_date = order.transaction_date
+			invoice.bill_date = order.transaction_date
+
+			if invoice.get("payment_schedule"):
+				invoice.payment_schedule[0].due_date = order.transaction_date
+
 			invoice.update_stock = 1
 			invoice.submit()