add back removed test

Signed-off-by: Ben Ye <[email protected]>

Author: yeya24

pkg/distributor/distributor_test.go

@@ -1777,6 +1777,32 @@ func BenchmarkDistributor_Push(b *testing.B) {
 			},
 			expectedErr: "labels size bytes exceeded",
 		},
+		"timestamp too old": {
+			prepareConfig: func(limits *validation.Limits) {
+				limits.RejectOldSamples = true
+				limits.RejectOldSamplesMaxAge = model.Duration(time.Hour)
+			},
+			prepareSeries: func() ([]labels.Labels, []cortexpb.Sample) {
+				metrics := make([]labels.Labels, numSeriesPerRequest)
+				samples := make([]cortexpb.Sample, numSeriesPerRequest)
+
+				for i := 0; i < numSeriesPerRequest; i++ {
+					lbls := labels.NewBuilder(labels.Labels{{Name: model.MetricNameLabel, Value: "foo"}})
+					for i := 0; i < 10; i++ {
+						lbls.Set(fmt.Sprintf("name_%d", i), fmt.Sprintf("value_%d", i))
+					}
+
+					metrics[i] = lbls.Labels(nil)
+					samples[i] = cortexpb.Sample{
+						Value:       float64(i),
+						TimestampMs: time.Now().Add(-2*time.Hour).UnixNano() / int64(time.Millisecond),
+					}
+				}
+
+				return metrics, samples
+			},
+			expectedErr: "timestamp too old",
+		},
 		"timestamp too new": {
 			prepareConfig: func(limits *validation.Limits) {
 				limits.CreationGracePeriod = model.Duration(time.Minute)