1 files changed, 74 insertions, 0 deletions
diff --git a/src/internal/trace/reader_test.go b/src/internal/trace/reader_test.go
index b395183e0e..222d2dfa82 100644
--- a/src/internal/trace/reader_test.go
+++ b/src/internal/trace/reader_test.go
@@ -13,6 +13,7 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+	"time"
 
 	"internal/trace"
 	"internal/trace/raw"
@@ -171,3 +172,76 @@ func dumpTraceToFile(t *testing.T, testName string, stress bool, b []byte) strin
 	}
 	return f.Name()
 }
+
+func TestTraceGenSync(t *testing.T) {
+	type sync struct {
+		Time          trace.Time
+		ClockSnapshot *trace.ClockSnapshot
+	}
+	runTest := func(testName string, wantSyncs []sync) {
+		t.Run(testName, func(t *testing.T) {
+			testPath := "testdata/tests/" + testName
+			r, _, _, err := testtrace.ParseFile(testPath)
+			if err != nil {
+				t.Fatalf("malformed test %s: bad trace file: %v", testPath, err)
+			}
+			tr, err := trace.NewReader(r)
+			if err != nil {
+				t.Fatalf("malformed test %s: bad trace file: %v", testPath, err)
+			}
+			var syncEvents []trace.Event
+			for {
+				ev, err := tr.ReadEvent()
+				if err == io.EOF {
+					break
+				}
+				if err != nil {
+					t.Fatalf("malformed test %s: bad trace file: %v", testPath, err)
+				}
+				if ev.Kind() == trace.EventSync {
+					syncEvents = append(syncEvents, ev)
+				}
+			}
+
+			if got, want := len(syncEvents), len(wantSyncs); got != want {
+				t.Errorf("got %d sync events, want %d", got, want)
+			}
+
+			for i, want := range wantSyncs {
+				got := syncEvents[i]
+				gotSync := syncEvents[i].Sync()
+				if got.Time() != want.Time {
+					t.Errorf("sync=%d got time %d, want %d", i+1, got.Time(), want.Time)
+				}
+				if gotSync.ClockSnapshot == nil && want.ClockSnapshot == nil {
+					continue
+				}
+				if gotSync.ClockSnapshot.Trace != want.ClockSnapshot.Trace {
+					t.Errorf("sync=%d got trace time %d, want %d", i+1, gotSync.ClockSnapshot.Trace, want.ClockSnapshot.Trace)
+				}
+				if !gotSync.ClockSnapshot.Wall.Equal(want.ClockSnapshot.Wall) {
+					t.Errorf("sync=%d got wall time %s, want %s", i+1, gotSync.ClockSnapshot.Wall, want.ClockSnapshot.Wall)
+				}
+				if gotSync.ClockSnapshot.Mono != want.ClockSnapshot.Mono {
+					t.Errorf("sync=%d got mono time %d, want %d", i+1, gotSync.ClockSnapshot.Mono, want.ClockSnapshot.Mono)
+				}
+			}
+		})
+	}
+
+	runTest("go123-sync.test", []sync{
+		{10, nil},
+		{40, nil},
+		// The EvFrequency batch for generation 3 is emitted at trace.Time(80),
+		// but 60 is the minTs of the generation, see b30 in the go generator.
+		{60, nil},
+		{63, nil},
+	})
+
+	runTest("go125-sync.test", []sync{
+		{9, &trace.ClockSnapshot{Trace: 10, Mono: 99, Wall: time.Date(2025, 2, 28, 15, 4, 9, 123, time.UTC)}},
+		{38, &trace.ClockSnapshot{Trace: 40, Mono: 199, Wall: time.Date(2025, 2, 28, 15, 4, 10, 123, time.UTC)}},
+		{58, &trace.ClockSnapshot{Trace: 60, Mono: 299, Wall: time.Date(2025, 2, 28, 15, 4, 11, 123, time.UTC)}},
+		{83, nil},
+	})
+}