once_test.go

Documentation: sync

		 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  }
		69
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