diff --git a/erpnext/crm/doctype/opportunity/test_opportunity.py b/erpnext/crm/doctype/opportunity/test_opportunity.py
index 62fad25a574..815ab992412 100644
--- a/erpnext/crm/doctype/opportunity/test_opportunity.py
+++ b/erpnext/crm/doctype/opportunity/test_opportunity.py
@@ -100,6 +100,42 @@ class TestOpportunity(ERPNextTestSuite):
 		opp.opportunity_owner = None
 		self.assertIsNone(opp.get_notification_email())
 
+	def test_declare_enquiry_lost(self):
+		lost_reason = _ensure_master("Opportunity Lost Reason", "lost_reason", "_Test Lost - Too Expensive")
+		competitor = _ensure_master("Competitor", "competitor_name", "_Test Competitor")
+
+		opp = make_opportunity(with_items=0)
+		opp.declare_enquiry_lost(
+			lost_reasons_list=[{"lost_reason": lost_reason}],
+			competitors=[{"competitor": competitor}],
+			detailed_reason="Budget too high",
+		)
+
+		opp.reload()
+		self.assertEqual(opp.status, "Lost")
+		self.assertEqual(opp.order_lost_reason, "Budget too high")
+		self.assertEqual([d.lost_reason for d in opp.lost_reasons], [lost_reason])
+		self.assertEqual([d.competitor for d in opp.competitors], [competitor])
+
+	def test_declare_lost_blocked_when_quotation_active(self):
+		opp = make_opportunity(with_items=0)
+		quotation = make_quotation(opp.name)
+		quotation.append("items", {"item_code": "_Test Item", "qty": 1})
+		quotation.run_method("set_missing_values")
+		quotation.run_method("calculate_taxes_and_totals")
+		quotation.submit()
+
+		# A submitted, still-active quotation exists, so the opportunity can't be marked lost
+		opp.reload()
+		self.assertRaises(frappe.ValidationError, opp.declare_enquiry_lost, [], [], "x")
+		self.assertNotEqual(opp.status, "Lost")
+
+
+def _ensure_master(doctype, fieldname, value):
+	if not frappe.db.exists(doctype, value):
+		frappe.get_doc({"doctype": doctype, fieldname: value}).insert(ignore_permissions=True)
+	return value
+
 
 def make_opportunity_from_lead(company):
 	new_lead_email_id = f"new{random_string(5)}@example.com"