diff --git a/erpnext/accounts/doctype/mode_of_payment/test_mode_of_payment.py b/erpnext/accounts/doctype/mode_of_payment/test_mode_of_payment.py
index 679bbb53386..c68597649dc 100644
--- a/erpnext/accounts/doctype/mode_of_payment/test_mode_of_payment.py
+++ b/erpnext/accounts/doctype/mode_of_payment/test_mode_of_payment.py
@@ -1,13 +1,66 @@
 # Copyright (c) 2015, Frappe Technologies Pvt. Ltd. and Contributors
 # See license.txt
 
+import unittest
+
 import frappe
 
 from erpnext.tests.utils import ERPNextTestSuite
 
+COMPANY = "_Test Company"
+
 
 class TestModeofPayment(ERPNextTestSuite):
-	pass
+	"""Mode of Payment validates its per-company default accounts (account company
+	must match the row, no company twice) and blocks disabling while a POS Profile
+	still references it."""
+
+	def setUp(self):
+		frappe.set_user("Administrator")
+
+	def make_mop(self, accounts=None, enabled=1):
+		doc = frappe.new_doc("Mode of Payment")
+		doc.mode_of_payment = f"_Test MoP {frappe.generate_hash(length=6)}"
+		doc.type = "General"
+		doc.enabled = enabled
+		for company, account in accounts or []:
+			doc.append("accounts", {"company": company, "default_account": account})
+		return doc
+
+	def test_valid_mode_of_payment_saves(self):
+		doc = self.make_mop(accounts=[(COMPANY, "Cash - _TC")])
+		doc.insert()
+		self.assertTrue(doc.name)
+
+	def test_account_of_wrong_company_throws(self):
+		other_account = frappe.get_all(
+			"Account", {"company": "_Test Company 1", "is_group": 0}, pluck="name"
+		)[0]
+		doc = self.make_mop(accounts=[(COMPANY, other_account)])
+		self.assertRaises(frappe.ValidationError, doc.insert)
+
+	def test_repeating_company_throws(self):
+		doc = self.make_mop(accounts=[(COMPANY, "Cash - _TC"), (COMPANY, "Debtors - _TC")])
+		self.assertRaises(frappe.ValidationError, doc.insert)
+
+	@unittest.expectedFailure
+	def test_disabling_mode_referenced_by_pos_profile_throws(self):
+		# SUSPECTED BUG: validate_pos_mode_of_payment queries "Sales Invoice Payment"
+		# rows with parenttype "POS Profile", but a POS Profile's payments are stored
+		# as "POS Payment Method" rows. The filter never matches, so the guard is dead
+		# and a mode still referenced by a POS Profile can be disabled. This asserts the
+		# intended behaviour; remove the xfail once the guard checks the right doctype.
+		from erpnext.accounts.doctype.pos_profile.test_pos_profile import make_pos_profile
+
+		make_pos_profile()  # its payments row references the "Cash" mode of payment
+		cash = frappe.get_doc("Mode of Payment", "Cash")
+		cash.enabled = 0
+		self.assertRaises(frappe.ValidationError, cash.save)
+
+	def test_disabling_unreferenced_mode_succeeds(self):
+		doc = self.make_mop(accounts=[(COMPANY, "Cash - _TC")], enabled=0)
+		doc.insert()
+		self.assertEqual(doc.enabled, 0)
 
 
 def set_default_account_for_mode_of_payment(mode_of_payment, company, account):