Repository: census-instrumentation/opencensus-go (go)

Issue:
ochttp public traceparent/tracestate marshal/unmarshal
**NB:** Before opening a feature request against this repo, consider whether the feature should/could be implemented in OpenCensus libraries in other languages. If so, please [open an issue on opencensus-specs](https://github.com/census-instrumentation/opencensus-specs/issues/new) first.



**Is your feature request related to a problem? Please describe.**
I wish to read and write traceparent/tracestate, encoded using [trace context](https://w3c.github.io/trace-context/), without passing an `http.Request`

**Describe the solution you'd like**
Two new methods should be added to [`HttpFormat`](https://github.com/census-instrumentation/opencensus-go/blob/master/plugin/ochttp/propagation/tracecontext/propagation.go#L46) or as public functions:

```
SpanContextFromHeaders(traceparent string, tracestate string) (sc trace.SpanContext, ok bool)
SpanContextToRequest(sc trace.SpanContext) (traceparent string, tracestate string)
```

**Describe alternatives you've considered**
AFAIK no alternatives are available in this library, except copy pasting that code in my own code.


Pull request:
Made public traceparent/tracestate marshal/unmarshal
Fix #1208

Signed-off-by: Francesco Guardiani <francescoguard@gmail.com>

Patch:
diff --git a/plugin/ocgrpc/client_metrics.go b/plugin/ocgrpc/client_metrics.go
index abe978b..49fde3d 100644
--- a/plugin/ocgrpc/client_metrics.go
+++ b/plugin/ocgrpc/client_metrics.go
@@ -60,6 +60,8 @@ var (
 		Aggregation: DefaultMillisecondsDistribution,
 	}
 
+	// Purposely reuses the count from `ClientRoundtripLatency`, tagging
+	// with method and status to result in ClientCompletedRpcs.
 	ClientCompletedRPCsView = &view.View{
 		Measure:     ClientRoundtripLatency,
 		Name:        "grpc.io/client/completed_rpcs",
diff --git a/plugin/ocgrpc/server_metrics.go b/plugin/ocgrpc/server_metrics.go
index 609d9ed..b205982 100644
--- a/plugin/ocgrpc/server_metrics.go
+++ b/plugin/ocgrpc/server_metrics.go
@@ -63,6 +63,8 @@ var (
 		Aggregation: DefaultMillisecondsDistribution,
 	}
 
+	// Purposely reuses the count from `ServerLatency`, tagging
+	// with method and status to result in ServerCompletedRpcs.
 	ServerCompletedRPCsView = &view.View{
 		Name:        "grpc.io/server/completed_rpcs",
 		Description: "Count of RPCs by method and status.",
diff --git a/plugin/ochttp/propagation/tracecontext/propagation.go b/plugin/ochttp/propagation/tracecontext/propagation.go
index 65ab1e9..48d8152 100644
--- a/plugin/ochttp/propagation/tracecontext/propagation.go
+++ b/plugin/ochttp/propagation/tracecontext/propagation.go
@@ -47,11 +47,17 @@ type HTTPFormat struct{}
 
 // SpanContextFromRequest extracts a span context from incoming requests.
 func (f *HTTPFormat) SpanContextFromRequest(req *http.Request) (sc trace.SpanContext, ok bool) {
-	h, ok := getRequestHeader(req, traceparentHeader, false)
-	if !ok {
+	tp, _ := getRequestHeader(req, traceparentHeader, false)
+	ts, _ := getRequestHeader(req, tracestateHeader, true)
+	return f.SpanContextFromHeaders(tp, ts)
+}
+
+// SpanContextFromHeaders extracts a span context from provided header values.
+func (f *HTTPFormat) SpanContextFromHeaders(tp string, ts string) (sc trace.SpanContext, ok bool) {
+	if tp == "" {
 		return trace.SpanContext{}, false
 	}
-	sections := strings.Split(h, "-")
+	sections := strings.Split(tp, "-")
 	if len(sections) < 4 {
 		return trace.SpanContext{}, false
 	}
@@ -101,7 +107,7 @@ func (f *HTTPFormat) SpanContextFromRequest(req *http.Request) (sc trace.SpanCon
 		return trace.SpanContext{}, false
 	}
 
-	sc.Tracestate = tracestateFromRequest(req)
+	sc.Tracestate = tracestateFromHeader(ts)
 	return sc, true
 }
 
@@ -128,14 +134,13 @@ func getRequestHeader(req *http.Request, name string, commaSeparated bool) (hdr
 // are resolved.
 // https://github.com/w3c/distributed-tracing/issues/172
 // https://github.com/w3c/distributed-tracing/issues/175
-func tracestateFromRequest(req *http.Request) *tracestate.Tracestate {
-	h, _ := getRequestHeader(req, tracestateHeader, true)
-	if h == "" {
+func tracestateFromHeader(ts string) *tracestate.Tracestate {
+	if ts == "" {
 		return nil
 	}
 
 	var entries []tracestate.Entry
-	pairs := strings.Split(h, ",")
+	pairs := strings.Split(ts, ",")
 	hdrLenWithoutOWS := len(pairs) - 1 // Number of commas
 	for _, pair := range pairs {
 		matches := trimOWSRegExp.FindStringSubmatch(pair)
@@ -153,15 +158,15 @@ func tracestateFromRequest(req *http.Request) *tracestate.Tracestate {
 		}
 		entries = append(entries, tracestate.Entry{Key: kv[0], Value: kv[1]})
 	}
-	ts, err := tracestate.New(nil, entries...)
+	tsParsed, err := tracestate.New(nil, entries...)
 	if err != nil {
 		return nil
 	}
 
-	return ts
+	return tsParsed
 }
 
-func tracestateToRequest(sc trace.SpanContext, req *http.Request) {
+func tracestateToHeader(sc trace.SpanContext) string {
 	var pairs = make([]string, 0, len(sc.Tracestate.Entries()))
 	if sc.Tracestate != nil {
 		for _, entry := range sc.Tracestate.Entries() {
@@ -170,18 +175,28 @@ func tracestateToRequest(sc trace.SpanContext, req *http.Request) {
 		h := strings.Join(pairs, ",")
 
 		if h != "" && len(h) <= maxTracestateLen {
-			req.Header.Set(tracestateHeader, h)
+			return h
 		}
 	}
+	return ""
 }
 
-// SpanContextToRequest modifies the given request to include traceparent and tracestate headers.
-func (f *HTTPFormat) SpanContextToRequest(sc trace.SpanContext, req *http.Request) {
-	h := fmt.Sprintf("%x-%x-%x-%x",
+// SpanContextToHeaders serialize the SpanContext to traceparent and tracestate headers.
+func (f *HTTPFormat) SpanContextToHeaders(sc trace.SpanContext) (tp string, ts string) {
+	tp = fmt.Sprintf("%x-%x-%x-%x",
 		[]byte{supportedVersion},
 		sc.TraceID[:],
 		sc.SpanID[:],
 		[]byte{byte(sc.TraceOptions)})
-	req.Header.Set(traceparentHeader, h)
-	tracestateToRequest(sc, req)
+	ts = tracestateToHeader(sc)
+	return
+}
+
+// SpanContextToRequest modifies the given request to include traceparent and tracestate headers.
+func (f *HTTPFormat) SpanContextToRequest(sc trace.SpanContext, req *http.Request) {
+	tp, ts := f.SpanContextToHeaders(sc)
+	req.Header.Set(traceparentHeader, tp)
+	if ts != "" {
+		req.Header.Set(tracestateHeader, ts)
+	}
 }
diff --git a/stats/view/aggregation.go b/stats/view/aggregation.go
index 9d70937..748bd56 100644
--- a/stats/view/aggregation.go
+++ b/stats/view/aggregation.go
@@ -15,6 +15,8 @@
 
 package view
 
+import "time"
+
 // AggType represents the type of aggregation function used on a View.
 type AggType int
 
@@ -45,20 +47,20 @@ type Aggregation struct {
 	Type    AggType   // Type is the AggType of this Aggregation.
 	Buckets []float64 // Buckets are the bucket endpoints if this Aggregation represents a distribution, see Distribution.
 
-	newData func() AggregationData
+	newData func(time.Time) AggregationData
 }
 
 var (
 	aggCount = &Aggregation{
 		Type: AggTypeCount,
-		newData: func() AggregationData {
-			return &CountData{}
+		newData: func(t time.Time) AggregationData {
+			return &CountData{Start: t}
 		},
 	}
 	aggSum = &Aggregation{
 		Type: AggTypeSum,
-		newData: func() AggregationData {
-			return &SumData{}
+		newData: func(t time.Time) AggregationData {
+			return &SumData{Start: t}
 		},
 	}
 )
@@ -103,8 +105,8 @@ func Distribution(bounds ...float64) *Aggregation {
 		Type:    AggTypeDistribution,
 		Buckets: bounds,
 	}
-	agg.newData = func() AggregationData {
-		return newDistributionData(agg)
+	agg.newData = func(t time.Time) AggregationData {
+		return newDistributionData(agg, t)
 	}
 	return agg
 }
@@ -114,7 +116,7 @@ func Distribution(bounds ...float64) *Aggregation {
 func LastValue() *Aggregation {
 	return &Aggregation{
 		Type: AggTypeLastValue,
-		newData: func() AggregationData {
+		newData: func(_ time.Time) AggregationData {
 			return &LastValueData{}
 		},
 	}
diff --git a/stats/view/aggregation_data.go b/stats/view/aggregation_data.go
index f331d45..d93b520 100644
--- a/stats/view/aggregation_data.go
+++ b/stats/view/aggregation_data.go
@@ -31,6 +31,7 @@ type AggregationData interface {
 	clone() AggregationData
 	equal(other AggregationData) bool
 	toPoint(t metricdata.Type, time time.Time) metricdata.Point
+	StartTime() time.Time
 }
 
 const epsilon = 1e-9
@@ -40,6 +41,7 @@ const epsilon = 1e-9
 //
 // Most users won't directly access count data.
 type CountData struct {
+	Start time.Time
 	Value int64
 }
 
@@ -50,7 +52,7 @@ func (a *CountData) addSample(_ float64, _ map[string]interface{}, _ time.Time)
 }
 
 func (a *CountData) clone() AggregationData {
-	return &CountData{Value: a.Value}
+	return &CountData{Value: a.Value, Start: a.Start}
 }
 
 func (a *CountData) equal(other AggregationData) bool {
@@ -59,7 +61,7 @@ func (a *CountData) equal(other AggregationData) bool {
 		return false
 	}
 
-	return a.Value == a2.Value
+	return a.Start.Equal(a2.Start) && a.Value == a2.Value
 }
 
 func (a *CountData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
@@ -71,11 +73,17 @@ func (a *CountData) toPoint(metricType metricdata.Type, t time.Time) metricdata.
 	}
 }
 
+// StartTime returns the start time of the data being aggregated by CountData.
+func (a *CountData) StartTime() time.Time {
+	return a.Start
+}
+
 // SumData is the aggregated data for the Sum aggregation.
 // A sum aggregation processes data and sums up the recordings.
 //
 // Most users won't directly access sum data.
 type SumData struct {
+	Start time.Time
 	Value float64
 }
 
@@ -86,7 +94,7 @@ func (a *SumData) addSample(v float64, _ map[string]interface{}, _ time.Time) {
 }
 
 func (a *SumData) clone() AggregationData {
-	return &SumData{Value: a.Value}
+	return &SumData{Value: a.Value, Start: a.Start}
 }
 
 func (a *SumData) equal(other AggregationData) bool {
@@ -94,7 +102,7 @@ func (a *SumData) equal(other AggregationData) bool {
 	if !ok {
 		return false
 	}
-	return math.Pow(a.Value-a2.Value, 2) < epsilon
+	return a.Start.Equal(a2.Start) && math.Pow(a.Value-a2.Value, 2) < epsilon
 }
 
 func (a *SumData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
@@ -108,6 +116,11 @@ func (a *SumData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Po
 	}
 }
 
+// StartTime returns the start time of the data being aggregated by SumData.
+func (a *SumData) StartTime() time.Time {
+	return a.Start
+}
+
 // DistributionData is the aggregated data for the
 // Distribution aggregation.
 //
@@ -126,9 +139,10 @@ type DistributionData struct {
 	// an exemplar for the associated bucket, or nil.
 	ExemplarsPerBucket []*metricdata.Exemplar
 	bounds             []float64 // histogram distribution of the values
+	Start              time.Time
 }
 
-func newDistributionData(agg *Aggregation) *DistributionData {
+func newDistributionData(agg *Aggregation, t time.Time) *DistributionData {
 	bucketCount := len(agg.Buckets) + 1
 	return &DistributionData{
 		CountPerBucket:     make([]int64, bucketCount),
@@ -136,6 +150,7 @@ func newDistributionData(agg *Aggregation) *DistributionData {
 		bounds:             agg.Buckets,
 		Min:                math.MaxFloat64,
 		Max:                math.SmallestNonzeroFloat64,
+		Start:              t,
 	}
 }
 
@@ -226,7 +241,11 @@ func (a *DistributionData) equal(other AggregationData) bool {
 			return false
 		}
 	}
-	return a.Count == a2.Count && a.Min == a2.Min && a.Max == a2.Max && math.Pow(a.Mean-a2.Mean, 2) < epsilon && math.Pow(a.variance()-a2.variance(), 2) < epsilon
+	return a.Start.Equal(a2.Start) &&
+		a.Count == a2.Count &&
+		a.Min == a2.Min &&
+		a.Max == a2.Max &&
+		math.Pow(a.Mean-a2.Mean, 2) < epsilon && math.Pow(a.variance()-a2.variance(), 2) < epsilon
 }
 
 func (a *DistributionData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
@@ -256,6 +275,11 @@ func (a *DistributionData) toPoint(metricType metricdata.Type, t time.Time) metr
 	}
 }
 
+// StartTime returns the start time of the data being aggregated by DistributionData.
+func (a *DistributionData) StartTime() time.Time {
+	return a.Start
+}
+
 // LastValueData returns the last value recorded for LastValue aggregation.
 type LastValueData struct {
 	Value float64
@@ -291,3 +315,22 @@ func (l *LastValueData) toPoint(metricType metricdata.Type, t time.Time) metricd
 		panic("unsupported metricdata.Type")
 	}
 }
+
+// StartTime returns an empty time value as start time is not recorded when using last value
+// aggregation.
+func (l *LastValueData) StartTime() time.Time {
+	return time.Time{}
+}
+
+// ClearStart clears the Start field from data if present. Useful for testing in cases where the
+// start time will be nondeterministic.
+func ClearStart(data AggregationData) {
+	switch data := data.(type) {
+	case *CountData:
+		data.Start = time.Time{}
+	case *SumData:
+		data.Start = time.Time{}
+	case *DistributionData:
+		data.Start = time.Time{}
+	}
+}
diff --git a/stats/view/collector.go b/stats/view/collector.go
index 8a6a2c0..ac22c93 100644
--- a/stats/view/collector.go
+++ b/stats/view/collector.go
@@ -35,7 +35,7 @@ type collector struct {
 func (c *collector) addSample(s string, v float64, attachments map[string]interface{}, t time.Time) {
 	aggregator, ok := c.signatures[s]
 	if !ok {
-		aggregator = c.a.newData()
+		aggregator = c.a.newData(t)
 		c.signatures[s] = aggregator
 	}
 	aggregator.addSample(v, attachments, t)
diff --git a/stats/view/view_to_metric.go b/stats/view/view_to_metric.go
index 5e1656a..57d615e 100644
--- a/stats/view/view_to_metric.go
+++ b/stats/view/view_to_metric.go
@@ -119,20 +119,15 @@ func toLabelValues(row *Row, expectedKeys []metricdata.LabelKey) []metricdata.La
 	return labelValues
 }
 
-func rowToTimeseries(v *viewInternal, row *Row, now time.Time, startTime time.Time) *metricdata.TimeSeries {
+func rowToTimeseries(v *viewInternal, row *Row, now time.Time) *metricdata.TimeSeries {
 	return &metricdata.TimeSeries{
 		Points:      []metricdata.Point{row.Data.toPoint(v.metricDescriptor.Type, now)},
 		LabelValues: toLabelValues(row, v.metricDescriptor.LabelKeys),
-		StartTime:   startTime,
+		StartTime:   row.Data.StartTime(),
 	}
 }
 
-func viewToMetric(v *viewInternal, r *resource.Resource, now time.Time, startTime time.Time) *metricdata.Metric {
-	if v.metricDescriptor.Type == metricdata.TypeGaugeInt64 ||
-		v.metricDescriptor.Type == metricdata.TypeGaugeFloat64 {
-		startTime = time.Time{}
-	}
-
+func viewToMetric(v *viewInternal, r *resource.Resource, now time.Time) *metricdata.Metric {
 	rows := v.collectedRows()
 	if len(rows) == 0 {
 		return nil
@@ -140,7 +135,7 @@ func viewToMetric(v *viewInternal, r *resource.Resource, now time.Time, startTim
 
 	ts := []*metricdata.TimeSeries{}
 	for _, row := range rows {
-		ts = append(ts, rowToTimeseries(v, row, now, startTime))
+		ts = append(ts, rowToTimeseries(v, row, now))
 	}
 
 	m := &metricdata.Metric{
diff --git a/stats/view/worker.go b/stats/view/worker.go
index ab8bfd4..6e8d18b 100644
--- a/stats/view/worker.go
+++ b/stats/view/worker.go
@@ -41,9 +41,9 @@ type measureRef struct {
 }
 
 type worker struct {
-	measures   map[string]*measureRef
-	views      map[string]*viewInternal
-	startTimes map[*viewInternal]time.Time
+	measures       map[string]*measureRef
+	views          map[string]*viewInternal
+	viewStartTimes map[*viewInternal]time.Time
 
 	timer      *time.Ticker
 	c          chan command
@@ -244,13 +244,13 @@ func (w *worker) SetReportingPeriod(d time.Duration) {
 // a single process.
 func NewMeter() Meter {
 	return &worker{
-		measures:   make(map[string]*measureRef),
-		views:      make(map[string]*viewInternal),
-		startTimes: make(map[*viewInternal]time.Time),
-		timer:      time.NewTicker(defaultReportingDuration),
-		c:          make(chan command, 1024),
-		quit:       make(chan bool),
-		done:       make(chan bool),
+		measures:       make(map[string]*measureRef),
+		views:          make(map[string]*viewInternal),
+		viewStartTimes: make(map[*viewInternal]time.Time),
+		timer:          time.NewTicker(defaultReportingDuration),
+		c:              make(chan command, 1024),
+		quit:           make(chan bool),
+		done:           make(chan bool),
 
 		exporters: make(map[Exporter]struct{}),
 	}
@@ -324,7 +324,7 @@ func (w *worker) tryRegisterView(v *View) (*viewInternal, error) {
 		return x, nil
 	}
 	w.views[vi.view.Name] = vi
-	w.startTimes[vi] = time.Now()
+	w.viewStartTimes[vi] = time.Now()
 	ref := w.getMeasureRef(vi.view.Measure.Name())
 	ref.views[vi] = struct{}{}
 	return vi, nil
@@ -334,7 +334,7 @@ func (w *worker) unregisterView(v *viewInternal) {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 	delete(w.views, v.view.Name)
-	delete(w.startTimes, v)
+	delete(w.viewStartTimes, v)
 	if measure := w.measures[v.view.Measure.Name()]; measure != nil {
 		delete(measure.views, v)
 	}
@@ -347,7 +347,7 @@ func (w *worker) reportView(v *viewInternal) {
 	rows := v.collectedRows()
 	viewData := &Data{
 		View:  v.view,
-		Start: w.startTimes[v],
+		Start: w.viewStartTimes[v],
 		End:   time.Now(),
 		Rows:  rows,
 	}
@@ -371,15 +371,7 @@ func (w *worker) toMetric(v *viewInternal, now time.Time) *metricdata.Metric {
 		return nil
 	}
 
-	var startTime time.Time
-	if v.metricDescriptor.Type == metricdata.TypeGaugeInt64 ||
-		v.metricDescriptor.Type == metricdata.TypeGaugeFloat64 {
-		startTime = time.Time{}
-	} else {
-		startTime = w.startTimes[v]
-	}
-
-	return viewToMetric(v, w.r, now, startTime)
+	return viewToMetric(v, w.r, now)
 }
 
 // Read reads all view data and returns them as metrics.


Test patch:
diff --git a/plugin/ocgrpc/client_stats_handler_test.go b/plugin/ocgrpc/client_stats_handler_test.go
index 7a2c366..d271b40 100644
--- a/plugin/ocgrpc/client_stats_handler_test.go
+++ b/plugin/ocgrpc/client_stats_handler_test.go
@@ -318,6 +318,9 @@ func TestClientDefaultCollections(t *testing.T) {
 				t.Errorf("%q: RetrieveData(%q) = %v", tc.label, wantData.v().Name, err)
 				continue
 			}
+			for i := range gotRows {
+				view.ClearStart(gotRows[i].Data)
+			}
 
 			for _, gotRow := range gotRows {
 				if !containsRow(wantData.rows, gotRow) {
diff --git a/plugin/ocgrpc/server_stats_handler_test.go b/plugin/ocgrpc/server_stats_handler_test.go
index fb45bb6..ab14f63 100644
--- a/plugin/ocgrpc/server_stats_handler_test.go
+++ b/plugin/ocgrpc/server_stats_handler_test.go
@@ -305,6 +305,10 @@ func TestServerDefaultCollections(t *testing.T) {
 				continue
 			}
 
+			for i := range gotRows {
+				view.ClearStart(gotRows[i].Data)
+			}
+
 			for _, gotRow := range gotRows {
 				if !containsRow(wantData.rows, gotRow) {
 					t.Errorf("%q: unwanted row for view %q: %v", tc.label, wantData.v().Name, gotRow)
diff --git a/plugin/ochttp/propagation/tracecontext/propagation_test.go b/plugin/ochttp/propagation/tracecontext/propagation_test.go
index 996cfa8..5489ba9 100644
--- a/plugin/ochttp/propagation/tracecontext/propagation_test.go
+++ b/plugin/ochttp/propagation/tracecontext/propagation_test.go
@@ -100,6 +100,14 @@ func TestHTTPFormat_FromRequest(t *testing.T) {
 			if gotOk != tt.wantOk {
 				t.Errorf("HTTPFormat.FromRequest() gotOk = %v, want %v", gotOk, tt.wantOk)
 			}
+
+			gotSc, gotOk = f.SpanContextFromHeaders(tt.header, "")
+			if !reflect.DeepEqual(gotSc, tt.wantSc) {
+				t.Errorf("HTTPFormat.SpanContextFromHeaders() gotTs = %v, want %v", gotSc.Tracestate, tt.wantSc.Tracestate)
+			}
+			if gotOk != tt.wantOk {
+				t.Errorf("HTTPFormat.SpanContextFromHeaders() gotOk = %v, want %v", gotOk, tt.wantOk)
+			}
 		})
 	}
 }
@@ -128,6 +136,11 @@ func TestHTTPFormat_ToRequest(t *testing.T) {
 			if got, want := h, tt.wantHeader; got != want {
 				t.Errorf("HTTPFormat.ToRequest() header = %v, want %v", got, want)
 			}
+
+			gotTp, _ := f.SpanContextToHeaders(tt.sc)
+			if gotTp != tt.wantHeader {
+				t.Errorf("HTTPFormat.SpanContextToHeaders() tracestate header = %v, want %v", gotTp, tt.wantHeader)
+			}
 		})
 	}
 }
@@ -212,6 +225,14 @@ func TestHTTPFormatTracestate_FromRequest(t *testing.T) {
 			if gotOk != tt.wantOk {
 				t.Errorf("HTTPFormat.FromRequest() gotOk = %v, want %v", gotOk, tt.wantOk)
 			}
+
+			gotSc, gotOk = f.SpanContextFromHeaders(tt.tpHeader, tt.tsHeader)
+			if !reflect.DeepEqual(gotSc, tt.wantSc) {
+				t.Errorf("HTTPFormat.SpanContextFromHeaders() gotTs = %v, want %v", gotSc.Tracestate, tt.wantSc.Tracestate)
+			}
+			if gotOk != tt.wantOk {
+				t.Errorf("HTTPFormat.SpanContextFromHeaders() gotOk = %v, want %v", gotOk, tt.wantOk)
+			}
 		})
 	}
 }
@@ -262,6 +283,11 @@ func TestHTTPFormatTracestate_ToRequest(t *testing.T) {
 			if got, want := h, tt.wantHeader; got != want {
 				t.Errorf("HTTPFormat.ToRequest() tracestate header = %v, want %v", got, want)
 			}
+
+			_, gotTs := f.SpanContextToHeaders(tt.sc)
+			if gotTs != tt.wantHeader {
+				t.Errorf("HTTPFormat.SpanContextToHeaders() tracestate header = %v, want %v", gotTs, tt.wantHeader)
+			}
 		})
 	}
 }
diff --git a/plugin/ochttp/route_test.go b/plugin/ochttp/route_test.go
index 2efe23f..50b9bb3 100644
--- a/plugin/ochttp/route_test.go
+++ b/plugin/ochttp/route_test.go
@@ -53,6 +53,9 @@ func TestWithRouteTag(t *testing.T) {
 	view.Unregister(v) // trigger exporting
 
 	got := e.rowsForView("request_total")
+	for i := range got {
+		view.ClearStart(got[i].Data)
+	}
 	want := []*view.Row{
 		{Data: &view.CountData{Value: 1}, Tags: []tag.Tag{{Key: ochttp.KeyServerRoute, Value: "/a/"}}},
 	}
@@ -90,6 +93,9 @@ func TestSetRoute(t *testing.T) {
 	view.Unregister(v) // trigger exporting
 
 	got := e.rowsForView("request_total")
+	for i := range got {
+		view.ClearStart(got[i].Data)
+	}
 	want := []*view.Row{
 		{Data: &view.CountData{Value: 1}, Tags: []tag.Tag{{Key: ochttp.KeyServerRoute, Value: "/a/"}}},
 	}
diff --git a/stats/view/aggregation_data_test.go b/stats/view/aggregation_data_test.go
index 7d09a8f..d0f48cf 100644
--- a/stats/view/aggregation_data_test.go
+++ b/stats/view/aggregation_data_test.go
@@ -29,7 +29,7 @@ func TestDataClone(t *testing.T) {
 	agg := &Aggregation{
 		Buckets: []float64{1, 2, 3, 4},
 	}
-	dist := newDistributionData(agg)
+	dist := newDistributionData(agg, time.Time{})
 	dist.Count = 7
 	dist.Max = 11
 	dist.Min = 1
@@ -72,7 +72,7 @@ func TestDistributionData_addSample(t *testing.T) {
 	agg := &Aggregation{
 		Buckets: []float64{1, 2},
 	}
-	dd := newDistributionData(agg)
+	dd := newDistributionData(agg, time.Time{})
 	attachments1 := map[string]interface{}{"key1": "value1"}
 	t1 := time.Now()
 	dd.addSample(0.5, attachments1, t1)
diff --git a/stats/view/view_test.go b/stats/view/view_test.go
index 2a2bde4..23b234d 100644
--- a/stats/view/view_test.go
+++ b/stats/view/view_test.go
@@ -21,6 +21,7 @@ import (
 	"time"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
 
 	"go.opencensus.io/metric/metricdata"
 
@@ -51,6 +52,7 @@ func Test_View_MeasureFloat64_AggregationDistribution(t *testing.T) {
 	type record struct {
 		f    float64
 		tags []tagString
+		t    time.Time
 	}
 
 	type testCase struct {
@@ -59,18 +61,23 @@ func Test_View_MeasureFloat64_AggregationDistribution(t *testing.T) {
 		wantRows []*Row
 	}
 
+	now := time.Now()
+	ts := make([]time.Time, 7)
+	for i := range ts {
+		ts[i] = now.Add(time.Duration(i) * time.Second)
+	}
 	tcs := []testCase{
 		{
 			"1",
 			[]record{
-				{1, []tagString{{k1, "v1"}}},
-				{5, []tagString{{k1, "v1"}}},
+				{1, []tagString{{k1, "v1"}}, ts[0]},
+				{5, []tagString{{k1, "v1"}}, ts[1]},
 			},
 			[]*Row{
 				{
 					[]tag.Tag{{Key: k1, Value: "v1"}},
 					&DistributionData{
-						Count: 2, Min: 1, Max: 5, Mean: 3, SumOfSquaredDev: 8, CountPerBucket: []int64{1, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 2, Min: 1, Max: 5, Mean: 3, SumOfSquaredDev: 8, CountPerBucket: []int64{1, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[0],
 					},
 				},
 			},
@@ -78,20 +85,20 @@ func Test_View_MeasureFloat64_AggregationDistribution(t *testing.T) {
 		{
 			"2",
 			[]record{
-				{1, []tagString{{k1, "v1"}}},
-				{5, []tagString{{k2, "v2"}}},
+				{1, []tagString{{k1, "v1"}}, ts[0]},
+				{5, []tagString{{k2, "v2"}}, ts[1]},
 			},
 			[]*Row{
 				{
 					[]tag.Tag{{Key: k1, Value: "v1"}},
 					&DistributionData{
-						Count: 1, Min: 1, Max: 1, Mean: 1, CountPerBucket: []int64{1, 0}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 1, Min: 1, Max: 1, Mean: 1, CountPerBucket: []int64{1, 0}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[0],
 					},
 				},
 				{
 					[]tag.Tag{{Key: k2, Value: "v2"}},
 					&DistributionData{
-						Count: 1, Min: 5, Max: 5, Mean: 5, CountPerBucket: []int64{0, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 1, Min: 5, Max: 5, Mean: 5, CountPerBucket: []int64{0, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[1],
 					},
 				},
 			},
@@ -99,35 +106,35 @@ func Test_View_MeasureFloat64_AggregationDistribution(t *testing.T) {
 		{
 			"3",
 			[]record{
-				{1, []tagString{{k1, "v1"}}},
-				{5, []tagString{{k1, "v1"}, {k3, "v3"}}},
-				{1, []tagString{{k1, "v1 other"}}},
-				{5, []tagString{{k2, "v2"}}},
-				{5, []tagString{{k1, "v1"}, {k2, "v2"}}},
+				{1, []tagString{{k1, "v1"}}, ts[0]},
+				{5, []tagString{{k1, "v1"}, {k3, "v3"}}, ts[1]},
+				{1, []tagString{{k1, "v1 other"}}, ts[2]},
+				{5, []tagString{{k2, "v2"}}, ts[3]},
+				{5, []tagString{{k1, "v1"}, {k2, "v2"}}, ts[4]},
 			},
 			[]*Row{
 				{
 					[]tag.Tag{{Key: k1, Value: "v1"}},
 					&DistributionData{
-						Count: 2, Min: 1, Max: 5, Mean: 3, SumOfSquaredDev: 8, CountPerBucket: []int64{1, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 2, Min: 1, Max: 5, Mean: 3, SumOfSquaredDev: 8, CountPerBucket: []int64{1, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[0],
 					},
 				},
 				{
 					[]tag.Tag{{Key: k1, Value: "v1 other"}},
 					&DistributionData{
-						Count: 1, Min: 1, Max: 1, Mean: 1, CountPerBucket: []int64{1, 0}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 1, Min: 1, Max: 1, Mean: 1, CountPerBucket: []int64{1, 0}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[2],
 					},
 				},
 				{
 					[]tag.Tag{{Key: k2, Value: "v2"}},
 					&DistributionData{
-						Count: 1, Min: 5, Max: 5, Mean: 5, CountPerBucket: []int64{0, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 1, Min: 5, Max: 5, Mean: 5, CountPerBucket: []int64{0, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[3],
 					},
 				},
 				{
 					[]tag.Tag{{Key: k1, Value: "v1"}, {Key: k2, Value: "v2"}},
 					&DistributionData{
-						Count: 1, Min: 5, Max: 5, Mean: 5, CountPerBucket: []int64{0, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 1, Min: 5, Max: 5, Mean: 5, CountPerBucket: []int64{0, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[4],
 					},
 				},
 			},
@@ -135,31 +142,31 @@ func Test_View_MeasureFloat64_AggregationDistribution(t *testing.T) {
 		{
 			"4",
 			[]record{
-				{1, []tagString{{k1, "v1 is a very long value key"}}},
-				{5, []tagString{{k1, "v1 is a very long value key"}, {k3, "v3"}}},
-				{1, []tagString{{k1, "v1 is another very long value key"}}},
-				{1, []tagString{{k1, "v1 is a very long value key"}, {k2, "v2 is a very long value key"}}},
-				{5, []tagString{{k1, "v1 is a very long value key"}, {k2, "v2 is a very long value key"}}},
-				{3, []tagString{{k1, "v1 is a very long value key"}, {k2, "v2 is a very long value key"}}},
-				{3, []tagString{{k1, "v1 is a very long value key"}, {k2, "v2 is a very long value key"}}},
+				{1, []tagString{{k1, "v1 is a very long value key"}}, ts[0]},
+				{5, []tagString{{k1, "v1 is a very long value key"}, {k3, "v3"}}, ts[1]},
+				{1, []tagString{{k1, "v1 is another very long value key"}}, ts[2]},
+				{1, []tagString{{k1, "v1 is a very long value key"}, {k2, "v2 is a very long value key"}}, ts[3]},
+				{5, []tagString{{k1, "v1 is a very long value key"}, {k2, "v2 is a very long value key"}}, ts[4]},
+				{3, []tagString{{k1, "v1 is a very long value key"}, {k2, "v2 is a very long value key"}}, ts[5]},
+				{3, []tagString{{k1, "v1 is a very long value key"}, {k2, "v2 is a very long value key"}}, ts[6]},
 			},
 			[]*Row{
 				{
 					[]tag.Tag{{Key: k1, Value: "v1 is a very long value key"}},
 					&DistributionData{
-						Count: 2, Min: 1, Max: 5, Mean: 3, SumOfSquaredDev: 8, CountPerBucket: []int64{1, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 2, Min: 1, Max: 5, Mean: 3, SumOfSquaredDev: 8, CountPerBucket: []int64{1, 1}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[0],
 					},
 				},
 				{
 					[]tag.Tag{{Key: k1, Value: "v1 is another very long value key"}},
 					&DistributionData{
-						Count: 1, Min: 1, Max: 1, Mean: 1, CountPerBucket: []int64{1, 0}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 1, Min: 1, Max: 1, Mean: 1, CountPerBucket: []int64{1, 0}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[2],
 					},
 				},
 				{
 					[]tag.Tag{{Key: k1, Value: "v1 is a very long value key"}, {Key: k2, Value: "v2 is a very long value key"}},
 					&DistributionData{
-						Count: 4, Min: 1, Max: 5, Mean: 3, SumOfSquaredDev: 2.66666666666667 * 3, CountPerBucket: []int64{1, 3}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil},
+						Count: 4, Min: 1, Max: 5, Mean: 3, SumOfSquaredDev: 2.66666666666667 * 3, CountPerBucket: []int64{1, 3}, bounds: []float64{2}, ExemplarsPerBucket: []*metricdata.Exemplar{nil, nil}, Start: ts[3],
 					},
 				},
 			},
@@ -178,22 +185,13 @@ func Test_View_MeasureFloat64_AggregationDistribution(t *testing.T) {
 			if err != nil {
 				t.Errorf("%v: New = %v", tc.label, err)
 			}
-			view.addSample(tag.FromContext(ctx), r.f, nil, time.Now())
+			view.addSample(tag.FromContext(ctx), r.f, nil, r.t)
 		}
 
 		gotRows := view.collectedRows()
-		for i, got := range gotRows {
-			if !containsRow(tc.wantRows, got) {
-				t.Errorf("%v-%d: got row %v; want none", tc.label, i, got)
-				break
-			}
-		}
-
-		for i, want := range tc.wantRows {
-			if !containsRow(gotRows, want) {
-				t.Errorf("%v-%d: got none; want row %v", tc.label, i, want)
-				break
-			}
+		if diff := cmp.Diff(gotRows, tc.wantRows, cmpopts.SortSlices(cmpRow)); diff != "" {
+			t.Errorf("%v: unexpected row (got-, want+): %s", tc.label, diff)
+			break
 		}
 	}
 }
@@ -215,8 +213,14 @@ func Test_View_MeasureFloat64_AggregationSum(t *testing.T) {
 	type record struct {
 		f    float64
 		tags []tagString
+		t    time.Time
 	}
 
+	now := time.Now()
+	ts := make([]time.Time, 5)
+	for i := range ts {
+		ts[i] = now.Add(time.Duration(i) * time.Second)
+	}
 	tcs := []struct {
 		label    string
 		records  []record
@@ -225,58 +229,58 @@ func Test_View_MeasureFloat64_AggregationSum(t *testing.T) {
 		{
 			"1",
 			[]record{
-				{1, []tagString{{k1, "v1"}}},
-				{5, []tagString{{k1, "v1"}}},
+				{1, []tagString{{k1, "v1"}}, ts[0]},
+				{5, []tagString{{k1, "v1"}}, ts[1]},
 			},
 			[]*Row{
 				{
 					[]tag.Tag{{Key: k1, Value: "v1"}},
-					&SumData{Value: 6},
+					&SumData{Value: 6, Start: ts[0]},
 				},
 			},
 		},
 		{
 			"2",
 			[]record{
-				{1, []tagString{{k1, "v1"}}},
-				{5, []tagString{{k2, "v2"}}},
+				{1, []tagString{{k1, "v1"}}, ts[0]},
+				{5, []tagString{{k2, "v2"}}, ts[1]},
 			},
 			[]*Row{
 				{
 					[]tag.Tag{{Key: k1, Value: "v1"}},
-					&SumData{Value: 1},
+					&SumData{Value: 1, Start: ts[0]},
 				},
 				{
 					[]tag.Tag{{Key: k2, Value: "v2"}},
-					&SumData{Value: 5},
+					&SumData{Value: 5, Start: ts[1]},
 				},
 			},
 		},
 		{
 			"3",
 			[]record{
-				{1, []tagString{{k1, "v1"}}},
-				{5, []tagString{{k1, "v1"}, {k3, "v3"}}},
-				{1, []tagString{{k1, "v1 other"}}},
-				{5, []tagString{{k2, "v2"}}},
-				{5, []tagString{{k1, "v1"}, {k2, "v2"}}},
+				{1, []tagString{{k1, "v1"}}, ts[0]},
+				{5, []tagString{{k1, "v1"}, {k3, "v3"}}, ts[1]},
+				{1, []tagString{{k1, "v1 other"}}, ts[2]},
+				{5, []tagString{{k2, "v2"}}, ts[3]},
+				{5, []tagString{{k1, "v1"}, {k2, "v2"}}, ts[4]},
 			},
 			[]*Row{
 				{
 					[]tag.Tag{{Key: k1, Value: "v1"}},
-					&SumData{Value: 6},
+					&SumData{Value: 6, Start: ts[0]},
 				},
 				{
 					[]tag.Tag{{Key: k1, Value: "v1 other"}},
-					&SumData{Value: 1},
+					&SumData{Value: 1, Start: ts[2]},
 				},
 				{
 					[]tag.Tag{{Key: k2, Value: "v2"}},
-					&SumData{Value: 5},
+					&SumData{Value: 5, Start: ts[3]},
 				},
 				{
 					[]tag.Tag{{Key: k1, Value: "v1"}, {Key: k2, Value: "v2"}},
-					&SumData{Value: 5},
+					&SumData{Value: 5, Start: ts[4]},
 				},
 			},
 		},
@@ -294,22 +298,13 @@ func Test_View_MeasureFloat64_AggregationSum(t *testing.T) {
 			if err != nil {
 				t.Errorf("%v: New = %v", tt.label, err)
 			}
-			view.addSample(tag.FromContext(ctx), r.f, nil, time.Now())
+			view.addSample(tag.FromContext(ctx), r.f, nil, r.t)
 		}
 
 		gotRows := view.collectedRows()
-		for i, got := range gotRows {
-			if !containsRow(tt.wantRows, got) {
-				t.Errorf("%v-%d: got row %v; want none", tt.label, i, got)
-				break
-			}
-		}
-
-		for i, want := range tt.wantRows {
-			if !containsRow(gotRows, want) {
-				t.Errorf("%v-%d: got none; want row %v", tt.label, i, want)
-				break
-			}
+		if diff := cmp.Diff(gotRows, tt.wantRows, cmpopts.SortSlices(cmpRow)); diff != "" {
+			t.Errorf("%v: unexpected row (got-, want+): %s", tt.label, diff)
+			break
 		}
 	}
 }
@@ -367,14 +362,8 @@ func TestViewSortedKeys(t *testing.T) {
 	}
 }
 
-// containsRow returns true if rows contain r.
-func containsRow(rows []*Row, r *Row) bool {
-	for _, x := range rows {
-		if r.Equal(x) {
-			return true
-		}
-	}
-	return false
+func cmpRow(r1 *Row, r2 *Row) bool {
+	return r1.Data.StartTime().Before(r2.Data.StartTime())
 }
 
 func TestRegisterUnregisterParity(t *testing.T) {
diff --git a/stats/view/view_to_metric_test.go b/stats/view/view_to_metric_test.go
index b6df3a0..e7676a6 100644
--- a/stats/view/view_to_metric_test.go
+++ b/stats/view/view_to_metric_test.go
@@ -253,7 +253,6 @@ func initMetricDescriptors() {
 }
 
 func Test_ViewToMetric(t *testing.T) {
-	startTime := time.Now().Add(-60 * time.Second)
 	now := time.Now()
 	tests := []*testToMetrics{
 		{
@@ -277,7 +276,7 @@ func Test_ViewToMetric(t *testing.T) {
 						},
 					},
 						LabelValues: labelValues,
-						StartTime:   startTime,
+						StartTime:   now,
 					},
 				},
 			},
@@ -305,7 +304,7 @@ func Test_ViewToMetric(t *testing.T) {
 							},
 						},
 						LabelValues: labelValues,
-						StartTime:   startTime,
+						StartTime:   now,
 					},
 				},
 			},
@@ -320,7 +319,7 @@ func Test_ViewToMetric(t *testing.T) {
 						metricdata.NewInt64Point(now, 2),
 					},
 						LabelValues: labelValues,
-						StartTime:   startTime,
+						StartTime:   now,
 					},
 				},
 			},
@@ -335,7 +334,7 @@ func Test_ViewToMetric(t *testing.T) {
 						metricdata.NewInt64Point(now, 2),
 					},
 						LabelValues: labelValues,
-						StartTime:   startTime,
+						StartTime:   now,
 					},
 				},
 			},
@@ -350,7 +349,7 @@ func Test_ViewToMetric(t *testing.T) {
 						metricdata.NewInt64Point(now, 6),
 					},
 						LabelValues: labelValues,
-						StartTime:   startTime,
+						StartTime:   now,
 					},
 				},
 			},
@@ -365,7 +364,7 @@ func Test_ViewToMetric(t *testing.T) {
 						metricdata.NewFloat64Point(now, 6.9),
 					},
 						LabelValues: labelValues,
-						StartTime:   startTime,
+						StartTime:   now,
 					},
 				},
 			},
@@ -417,12 +416,10 @@ func Test_ViewToMetric(t *testing.T) {
 		},
 	}
 
-	wantMetrics := []*metricdata.Metric{}
 	for _, tc := range tests {
 		tc.vi, _ = defaultWorker.tryRegisterView(tc.view)
 		tc.vi.clearRows()
 		tc.vi.subscribe()
-		wantMetrics = append(wantMetrics, tc.wantMetric)
 	}
 
 	for i, tc := range tests {
@@ -447,7 +444,7 @@ func Test_ViewToMetric(t *testing.T) {
 			tc.vi.addSample(tag.FromContext(ctx), v, nil, now)
 		}
 
-		gotMetric := viewToMetric(tc.vi, nil, now, startTime)
+		gotMetric := viewToMetric(tc.vi, nil, now)
 		if !cmp.Equal(gotMetric, tc.wantMetric) {
 			// JSON format is strictly for checking the content when test fails. Do not use JSON
 			// format to determine if the two values are same as it doesn't differentiate between
@@ -461,7 +458,6 @@ func Test_ViewToMetric(t *testing.T) {
 // Test to verify that a metric converted from a view with Aggregation Count should always
 // have Dimensionless unit.
 func TestUnitConversionForAggCount(t *testing.T) {
-	startTime := time.Now().Add(-60 * time.Second)
 	now := time.Now()
 	tests := []*struct {
 		name     string
@@ -509,7 +505,7 @@ func TestUnitConversionForAggCount(t *testing.T) {
 
 	for _, tc := range tests {
 		tc.vi.addSample(tag.FromContext(context.Background()), 5.0, nil, now)
-		gotMetric := viewToMetric(tc.vi, nil, now, startTime)
+		gotMetric := viewToMetric(tc.vi, nil, now)
 		gotUnit := gotMetric.Descriptor.Unit
 		if !cmp.Equal(gotUnit, tc.wantUnit) {
 			t.Errorf("Verify Unit: %s: Got:%v Want:%v", tc.name, gotUnit, tc.wantUnit)
diff --git a/stats/view/worker_test.go b/stats/view/worker_test.go
index 193aad0..fe8e35f 100644
--- a/stats/view/worker_test.go
+++ b/stats/view/worker_test.go
@@ -23,6 +23,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/google/go-cmp/cmp"
 	"go.opencensus.io/resource"
 
 	"go.opencensus.io/metric/metricdata"
@@ -213,12 +214,12 @@ func Test_Worker_MultiExport(t *testing.T) {
 			case *CountData:
 				got := ts.Points[0].Value.(int64)
 				if wantValue.Value != got {
-					t.Errorf("Mismatched value (want %d, got %d) for %v in %q", wantValue, got, ts, key)
+					t.Errorf("Mismatched value (want %d, got %d) for %v in %q", wantValue.Value, got, ts, key)
 				}
 			case *SumData:
 				got := ts.Points[0].Value.(float64)
 				if wantValue.Value != got {
-					t.Errorf("Mismatched value (want %f, got %f) for %v in %q", wantValue, got, ts, key)
+					t.Errorf("Mismatched value (want %f, got %f) for %v in %q", wantValue.Value, got, ts, key)
 				}
 			default:
 				t.Errorf("Unexpected type of data: %T for %v in %q", wantValue, want[i], key)
@@ -335,20 +336,22 @@ func Test_Worker_RecordFloat64(t *testing.T) {
 
 		for _, w := range tc.wants {
 			gotRows, err := RetrieveData(w.v.Name)
+			for i := range gotRows {
+				switch data := gotRows[i].Data.(type) {
+				case *CountData:
+					data.Start = time.Time{}
+				case *SumData:
+					data.Start = time.Time{}
+				case *DistributionData:
+					data.Start = time.Time{}
+				}
+			}
 			if (err != nil) != (w.err != nil) {
 				t.Fatalf("%s: RetrieveData(%v) = %v; want error = %v", tc.label, w.v.Name, err, w.err)
 			}
-			for _, got := range gotRows {
-				if !containsRow(w.rows, got) {
-					t.Errorf("%s: got row %#v; want none", tc.label, got)
-					break
-				}
-			}
-			for _, want := range w.rows {
-				if !containsRow(gotRows, want) {
-					t.Errorf("%s: got none; want %#v'", tc.label, want)
-					break
-				}
+			if diff := cmp.Diff(gotRows, w.rows); diff != "" {
+				t.Errorf("%v: unexpected row (got-, want+): %s", tc.label, diff)
+				break
 			}
 		}