libgo/go/sync/once_test.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package sync_test
   6
   7 import (
   8         . "sync"
   9         "testing"
  10 )
  11
  12 type one int
  13
  14 func (o *one) Increment() {
  15         *o++
  16 }
  17
  18 func run(t *testing.T, once *Once, o *one, c chan bool) {
  19         once.Do(func() { o.Increment() })
  20         if v := *o; v != 1 {
  21                 t.Errorf("once failed inside run: %d is not 1", v)
  22         }
  23         c <- true
  24 }
  25
  26 func TestOnce(t *testing.T) {
  27         o := new(one)
  28         once := new(Once)
  29         c := make(chan bool)
  30         const N = 10
  31         for i := 0; i < N; i++ {
  32                 go run(t, once, o, c)
  33         }
  34         for i := 0; i < N; i++ {
  35                 <-c
  36         }
  37         if *o != 1 {
  38                 t.Errorf("once failed outside run: %d is not 1", *o)
  39         }
  40 }
  41
  42 func TestOncePanic(t *testing.T) {
  43         var once Once
  44         func() {
  45                 defer func() {
  46                         if r := recover(); r == nil {
  47                                 t.Fatalf("Once.Do did not panic")
  48                         }
  49                 }()
  50                 once.Do(func() {
  51                         panic("failed")
  52                 })
  53         }()
  54
  55         once.Do(func() {
  56                 t.Fatalf("Once.Do called twice")
  57         })
  58 }
  59
  60 func BenchmarkOnce(b *testing.B) {
  61         var once Once
  62         f := func() {}
  63         b.RunParallel(func(pb *testing.PB) {
  64                 for pb.Next() {
  65                         once.Do(f)
  66                 }
  67         })
  68 }