libgo/go/net/dnsclient_test.go

   1 // Copyright 2014 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 net
   6
   7 import (
   8         "math/rand"
   9         "testing"
  10 )
  11
  12 func checkDistribution(t *testing.T, data []*SRV, margin float64) {
  13         sum := 0
  14         for _, srv := range data {
  15                 sum += int(srv.Weight)
  16         }
  17
  18         results := make(map[string]int)
  19
  20         count := 1000
  21         for j := 0; j < count; j++ {
  22                 d := make([]*SRV, len(data))
  23                 copy(d, data)
  24                 byPriorityWeight(d).shuffleByWeight()
  25                 key := d[0].Target
  26                 results[key] = results[key] + 1
  27         }
  28
  29         actual := results[data[0].Target]
  30         expected := float64(count) * float64(data[0].Weight) / float64(sum)
  31         diff := float64(actual) - expected
  32         t.Logf("actual: %v diff: %v e: %v m: %v", actual, diff, expected, margin)
  33         if diff < 0 {
  34                 diff = -diff
  35         }
  36         if diff > (expected * margin) {
  37                 t.Errorf("missed target weight: expected %v, %v", expected, actual)
  38         }
  39 }
  40
  41 func testUniformity(t *testing.T, size int, margin float64) {
  42         rand.Seed(1)
  43         data := make([]*SRV, size)
  44         for i := 0; i < size; i++ {
  45                 data[i] = &SRV{Target: string('a' + i), Weight: 1}
  46         }
  47         checkDistribution(t, data, margin)
  48 }
  49
  50 func TestUniformity(t *testing.T) {
  51         testUniformity(t, 2, 0.05)
  52         testUniformity(t, 3, 0.10)
  53         testUniformity(t, 10, 0.20)
  54         testWeighting(t, 0.05)
  55 }
  56
  57 func testWeighting(t *testing.T, margin float64) {
  58         rand.Seed(1)
  59         data := []*SRV{
  60                 {Target: "a", Weight: 60},
  61                 {Target: "b", Weight: 30},
  62                 {Target: "c", Weight: 10},
  63         }
  64         checkDistribution(t, data, margin)
  65 }
  66
  67 func TestWeighting(t *testing.T) {
  68         testWeighting(t, 0.05)
  69 }