test: address review feedback on Supplier Scorecard tests

- assert cost-of-shipments against the PO base_amount instead of a
  hardcoded total, so it holds when conversion_rate != 1
- guard the idempotency test's fixed scorecard name against leftovers
- clarify that the eval-statement zero/None substitution is a truthiness check

erpnext/buying/doctype/supplier_scorecard/test_supplier_scorecard.py

@@ -79,6 +79,7 @@ class TestSupplierScorecard(ERPNextTestSuite):
 		supplier = create_test_supplier("_Test Supplier SC Idempotent")
 		frappe.db.set_value("Supplier", supplier, "creation", add_days(nowdate(), -75))
 
+		frappe.delete_doc_if_exists("Supplier Scorecard", supplier)
 		doc = make_supplier_scorecard()
 		doc.supplier = supplier
 		doc.name = supplier

erpnext/buying/doctype/supplier_scorecard_period/test_supplier_scorecard_period.py

@@ -32,7 +32,8 @@ class TestSupplierScorecardPeriod(ERPNextTestSuite):
 				{"variable_label": "B", "param_name": "b", "path": "get_total_workdays", "value": 0},
 			]
 		)
-		# present value -> formatted; missing/zero value -> "0.0"
+		# get_eval_statement checks `if var.value:` (truthiness), so a falsy value -
+		# whether 0 or None - is substituted as "0.0", while a real value is formatted
 		self.assertEqual(period.get_eval_statement("{a} + {b}"), "5.00 + 0.0")
 
 	def test_period_score_is_weighted_sum_of_criteria(self):

erpnext/buying/doctype/supplier_scorecard_variable/test_supplier_scorecard_variable.py

@@ -35,11 +35,12 @@ class TestSupplierScorecardVariable(ERPNextTestSuite):
 
 	def test_total_cost_of_shipments_counts_only_in_period(self):
 		supplier = create_scorecard_supplier()
-		create_scorecard_po(supplier, nowdate(), qty=10, rate=100)  # in period -> 1000
+		in_period_po = create_scorecard_po(supplier, nowdate(), qty=10, rate=100)
 		create_scorecard_po(supplier, add_days(nowdate(), 60), qty=5, rate=100)  # outside period
 
 		scorecard = scorecard_for(supplier)
-		self.assertEqual(get_total_cost_of_shipments(scorecard), 1000)
+		# Compare against base_amount (not a hardcoded total) to stay correct if conversion_rate != 1
+		self.assertEqual(get_total_cost_of_shipments(scorecard), in_period_po.items[0].base_amount)
 
 	def test_on_time_and_delayed_shipments(self):
 		supplier = create_scorecard_supplier()