singleflight_test.go

Documentation: github.com/golang/groupcache/singleflight

     1  /*
     2  Copyright 2012 Google Inc.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8       http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package singleflight
    18  
    19  import (
    20  	"errors"
    21  	"fmt"
    22  	"sync"
    23  	"sync/atomic"
    24  	"testing"
    25  	"time"
    26  )
    27  
    28  func TestDo(t *testing.T) {
    29  	var g Group
    30  	v, err := g.Do("key", func() (interface{}, error) {
    31  		return "bar", nil
    32  	})
    33  	if got, want := fmt.Sprintf("%v (%T)", v, v), "bar (string)"; got != want {
    34  		t.Errorf("Do = %v; want %v", got, want)
    35  	}
    36  	if err != nil {
    37  		t.Errorf("Do error = %v", err)
    38  	}
    39  }
    40  
    41  func TestDoErr(t *testing.T) {
    42  	var g Group
    43  	someErr := errors.New("some error")
    44  	v, err := g.Do("key", func() (interface{}, error) {
    45  		return nil, someErr
    46  	})
    47  	if err != someErr {
    48  		t.Errorf("Do error = %v; want someErr", err)
    49  	}
    50  	if v != nil {
    51  		t.Errorf("unexpected non-nil value %#v", v)
    52  	}
    53  }
    54  
    55  func TestDoDupSuppress(t *testing.T) {
    56  	var g Group
    57  	c := make(chan string)
    58  	var calls int32
    59  	fn := func() (interface{}, error) {
    60  		atomic.AddInt32(&calls, 1)
    61  		return <-c, nil
    62  	}
    63  
    64  	const n = 10
    65  	var wg sync.WaitGroup
    66  	for i := 0; i < n; i++ {
    67  		wg.Add(1)
    68  		go func() {
    69  			v, err := g.Do("key", fn)
    70  			if err != nil {
    71  				t.Errorf("Do error: %v", err)
    72  			}
    73  			if v.(string) != "bar" {
    74  				t.Errorf("got %q; want %q", v, "bar")
    75  			}
    76  			wg.Done()
    77  		}()
    78  	}
    79  	time.Sleep(100 * time.Millisecond) // let goroutines above block
    80  	c <- "bar"
    81  	wg.Wait()
    82  	if got := atomic.LoadInt32(&calls); got != 1 {
    83  		t.Errorf("number of calls = %d; want 1", got)
    84  	}
    85  }
    86
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