test: fix pricelist tests (#26839)

problem: exchange rate API is returning exchange rates for "_Test currency".
These tests were relying on failure of that function.
diff --git a/erpnext/stock/doctype/batch/test_batch.py b/erpnext/stock/doctype/batch/test_batch.py
index cbd272d..a85a022 100644
--- a/erpnext/stock/doctype/batch/test_batch.py
+++ b/erpnext/stock/doctype/batch/test_batch.py
@@ -269,11 +269,14 @@
 		batch2 = create_batch('_Test Batch Price Item', 300, 1)
 		batch3 = create_batch('_Test Batch Price Item', 400, 0)
 
+		company = "_Test Company with perpetual inventory"
+		currency = frappe.get_cached_value("Company",  company,  "default_currency")
+
 		args = frappe._dict({
 			"item_code": "_Test Batch Price Item",
-			"company": "_Test Company with perpetual inventory",
+			"company": company,
 			"price_list": "_Test Price List",
-			"currency": "_Test Currency",
+			"currency": currency,
 			"doctype": "Sales Invoice",
 			"conversion_rate": 1,
 			"price_list_currency": "_Test Currency",
@@ -333,4 +336,4 @@
 	except frappe.DuplicateEntryError:
 		batch = frappe.get_doc("Batch", args.batch_id)
 
-	return batch
\ No newline at end of file
+	return batch
diff --git a/erpnext/stock/doctype/item/test_item.py b/erpnext/stock/doctype/item/test_item.py
index 922049f..7a9985d 100644
--- a/erpnext/stock/doctype/item/test_item.py
+++ b/erpnext/stock/doctype/item/test_item.py
@@ -83,14 +83,17 @@
 
 		make_test_objects("Item Price")
 
+		company = "_Test Company"
+		currency = frappe.get_cached_value("Company",  company,  "default_currency")
+
 		details = get_item_details({
 			"item_code": "_Test Item",
-			"company": "_Test Company",
+			"company": company,
 			"price_list": "_Test Price List",
-			"currency": "_Test Currency",
+			"currency": currency,
 			"doctype": "Sales Order",
 			"conversion_rate": 1,
-			"price_list_currency": "_Test Currency",
+			"price_list_currency": currency,
 			"plc_conversion_rate": 1,
 			"order_type": "Sales",
 			"customer": "_Test Customer",