Add some race-detector tests

filter/txnBuf/race_test.go

Index: filter/txnBuf/race_test.go
diff --git a/filter/txnBuf/race_test.go b/filter/txnBuf/race_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..8ad0734954a42754ee532b89ce411fd57fcdbdd9
--- /dev/null
+++ b/filter/txnBuf/race_test.go
@@ -0,0 +1,62 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package txnBuf
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/luci/gae/impl/memory"
+	"github.com/luci/gae/service/datastore"
+	"golang.org/x/net/context"
+)
+
+type Counter struct {
+	ID int64 `gae:"$id"`
+
+	Value int64
+}
+
+func TestRace(t *testing.T) {
+	t.Parallel()
+
+	c := FilterRDS(memory.Use(context.Background()))
+	ds := datastore.Get(c)
+
+	wg := sync.WaitGroup{}
+	for i := 0; i < 100; i++ {
+		id := int64(i + 1)
+
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			err := ds.RunInTransaction(func(c context.Context) error {
+				ds := datastore.Get(c)
+
+				for i := 0; i < 100; i++ {
+					err := ds.RunInTransaction(func(c context.Context) error {
+						ds := datastore.Get(c)
+
+						ctr := &Counter{ID: id}
+						if err := ds.Get(ctr); err != nil && err != datastore.ErrNoSuchEntity {
+							t.Fatal("bad Get", err)
+						}
+						ctr.Value++
+						return ds.Put(ctr)
+					}, nil)
+					if err != nil {
+						t.Fatal("bad inner RIT", err)
+					}
+				}
+
+				return nil
+			}, nil)
+			if err != nil {
+				t.Fatal("bad outer RIT", err)
+			}
+		}()
+	}
+	wg.Wait()
+}