promtool: alert_rule_test items require alertname

Accepting alert_rule_test without alertname is confusing as it will
always pass with empty exp_alerts, and never with non-empty exp_alerts.

Signed-off-by: Raphael Bauduin <[email protected]>

Author: Raphael Bauduin

cmd/promtool/unittest.go

@@ -188,6 +188,13 @@ func (tg *testGroup) test(evalInterval time.Duration, groupOrderMap map[string]i
 	// Map of all the unit tests for given eval_time.
 	alertTests := make(map[model.Duration][]alertTestCase)
 	for _, alert := range tg.AlertRuleTests {
+		if alert.Alertname == "" {
+			var testGroupLog string
+			if tg.TestGroupName != "" {
+				testGroupLog = fmt.Sprintf(" (in TestGroup %s)", tg.TestGroupName)
+			}
+			return []error{errors.Errorf("an item under alert_rule_test misses required attribute alertname at eval_time %v%s", alert.EvalTime, testGroupLog)}
+		}
 		alertEvalTimesMap[alert.EvalTime] = struct{}{}
 
 		if _, ok := alertsInTest[alert.EvalTime]; !ok {