test: add coverage for Negative Batch Report report

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

erpnext/stock/report/negative_batch_report/test_negative_batch_report.py

@@ -0,0 +1,54 @@
+# Copyright (c) 2026, Frappe Technologies Pvt. Ltd. and Contributors
+# See license.txt
+
+import frappe
+
+from erpnext.tests.utils import ERPNextTestSuite
+
+
+class TestNegativeBatchReport(ERPNextTestSuite):
+	def run_report(self, item_code):
+		from erpnext.stock.report.negative_batch_report.negative_batch_report import execute
+
+		return execute(
+			frappe._dict(
+				{
+					"company": "_Test Company",
+					"warehouse": "_Test Warehouse - _TC",
+					"item_code": item_code,
+				}
+			)
+		)[1]
+
+	def test_healthy_batch_not_negative(self):
+		from erpnext.stock.doctype.item.test_item import make_item
+		from erpnext.stock.doctype.stock_entry.stock_entry_utils import make_stock_entry
+
+		item = make_item(
+			properties={
+				"is_stock_item": 1,
+				"has_batch_no": 1,
+				"create_new_batch": 1,
+				"batch_number_series": "NBR-.#####",
+			}
+		).name
+
+		make_stock_entry(
+			item_code=item,
+			to_warehouse="_Test Warehouse - _TC",
+			qty=10,
+			rate=100,
+			posting_date="2026-06-01",
+		)
+		make_stock_entry(
+			item_code=item,
+			from_warehouse="_Test Warehouse - _TC",
+			qty=4,
+			posting_date="2026-06-02",
+		)
+
+		data = self.run_report(item)
+
+		# The batch was only received (10) before being issued (4), so its running
+		# balance never goes negative; the report must not list this item's batch.
+		self.assertFalse([row for row in data if row.get("item_code") == item])