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strings: fix flaky TestBuilderGrow test

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Fixes #24647

Change-Id: I79c2b45cf7fc9c0ed0c7a665472556bd248e7584
Reviewed-on: https://go-review.googlesource.com/104235
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
This commit is contained in:
Brad Fitzpatrick 2018-04-02 23:07:22 +00:00
parent da02dcda02
commit 071f0de4ec
1 changed files with 18 additions and 21 deletions
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39
src/strings/builder_test.go
View file

@ -6,7 +6,6 @@ package strings_test
import (
"bytes"
"runtime"
. "strings"
"testing"
)
@ -86,15 +85,21 @@ func TestBuilderReset(t *testing.T) {
func TestBuilderGrow(t *testing.T) {
for _, growLen := range []int{0, 100, 1000, 10000, 100000} {
var b Builder
b.Grow(growLen)
p := bytes.Repeat([]byte{'a'}, growLen)
allocs := numAllocs(func() { b.Write(p) })
if allocs > 0 {
t.Errorf("growLen=%d: allocation occurred during write", growLen)
allocs := testing.AllocsPerRun(100, func() {
var b Builder
b.Grow(growLen) // should be only alloc, when growLen > 0
b.Write(p)
if b.String() != string(p) {
t.Fatalf("growLen=%d: bad data written after Grow", growLen)
}
})
wantAllocs := 1
if growLen == 0 {
wantAllocs = 0
}
if b.String() != string(p) {
t.Errorf("growLen=%d: bad data written after Grow", growLen)
if g, w := int(allocs), wantAllocs; g != w {
t.Errorf("growLen=%d: got %d allocs during Write; want %v", growLen, g, w)
}
}
}
@ -168,13 +173,14 @@ func TestBuilderWriteByte(t *testing.T) {
func TestBuilderAllocs(t *testing.T) {
var b Builder
b.Grow(5)
const msg = "hello"
b.Grow(len(msg) * 2) // because AllocsPerRun does an extra "warm-up" iteration
var s string
allocs := numAllocs(func() {
allocs := int(testing.AllocsPerRun(1, func() {
b.WriteString("hello")
s = b.String()
})
if want := "hello"; s != want {
}))
if want := msg + msg; s != want {
t.Errorf("String: got %#q; want %#q", s, want)
}
if allocs > 0 {
@ -194,15 +200,6 @@ func TestBuilderAllocs(t *testing.T) {
}
}
func numAllocs(fn func()) uint64 {
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
var m1, m2 runtime.MemStats
runtime.ReadMemStats(&m1)
fn()
runtime.ReadMemStats(&m2)
return m2.Mallocs - m1.Mallocs
}
func TestBuilderCopyPanic(t *testing.T) {
tests := []struct {
name string