1 files changed, 60 insertions, 0 deletions
diff --git a/src/pkg/sync/waitgroup_test.go b/src/pkg/sync/waitgroup_test.go
new file mode 100644
index 000000000..fe35732e7
--- /dev/null
+++ b/src/pkg/sync/waitgroup_test.go
@@ -0,0 +1,60 @@
+// Copyright 2011 The Go 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 sync_test
+
+import (
+	. "sync"
+	"testing"
+)
+
+func testWaitGroup(t *testing.T, wg1 *WaitGroup, wg2 *WaitGroup) {
+	n := 16
+	wg1.Add(n)
+	wg2.Add(n)
+	exited := make(chan bool, n)
+	for i := 0; i != n; i++ {
+		go func(i int) {
+			wg1.Done()
+			wg2.Wait()
+			exited <- true
+		}(i)
+	}
+	wg1.Wait()
+	for i := 0; i != n; i++ {
+		select {
+		case <-exited:
+			t.Fatal("WaitGroup released group too soon")
+		default:
+		}
+		wg2.Done()
+	}
+	for i := 0; i != n; i++ {
+		<-exited // Will block if barrier fails to unlock someone.
+	}
+}
+
+func TestWaitGroup(t *testing.T) {
+	wg1 := &WaitGroup{}
+	wg2 := &WaitGroup{}
+
+	// Run the same test a few times to ensure barrier is in a proper state.
+	for i := 0; i != 8; i++ {
+		testWaitGroup(t, wg1, wg2)
+	}
+}
+
+func TestWaitGroupMisuse(t *testing.T) {
+	defer func() {
+		err := recover()
+		if err != "sync: negative WaitGroup count" {
+			t.Fatalf("Unexpected panic: %#v", err)
+		}
+	}()
+	wg := &WaitGroup{}
+	wg.Add(1)
+	wg.Done()
+	wg.Done()
+	t.Fatal("Should panic")
+}