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writerset_test.go
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writerset_test.go
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package writerset
import (
"bytes"
"errors"
"fmt"
"io"
"testing"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
)
func TestWriterset(t *testing.T) {
ws := WriterSet{}
bufA := &bytes.Buffer{}
bufB := &bytes.Buffer{}
bufC := &bytes.Buffer{}
flushableC := &flushWriter{w: bufC}
writeNoError(t, &ws, "0")
ws.Add(bufA)
writeNoError(t, &ws, "1")
ws.Add(bufB)
writeNoError(t, &ws, "2")
ws.Remove(bufA)
ws.Add(flushableC)
writeNoError(t, &ws, "3")
assert.Equal(t, "12", bufA.String())
assert.Equal(t, "23", bufB.String())
assert.Equal(t, "", bufC.String()) // should be empty until flush
ws.Flush()
assert.Equal(t, "12", bufA.String())
assert.Equal(t, "23", bufB.String())
assert.Equal(t, "3", bufC.String()) // should be pupulated after flush
assert.False(t, ws.Contains(bufA))
assert.True(t, ws.Contains(bufB))
assert.False(t, ws.Contains(bufC))
assert.True(t, ws.Contains(flushableC))
}
func writeNoError(t *testing.T, w io.Writer, s string) {
_, err := fmt.Fprint(w, s)
require.NoError(t, err)
}
type flushWriter struct {
buf bytes.Buffer
w io.Writer
}
func (fw *flushWriter) Write(b []byte) (int, error) {
return fw.buf.Write(b)
}
func (fw *flushWriter) Flush() {
_, _ = io.Copy(fw.w, &fw.buf)
}
func TestFail(t *testing.T) {
ws := WriterSet{}
bufA := &bytes.Buffer{}
bufB := &bytes.Buffer{}
bufC := &bytes.Buffer{}
failB := &failWriter{failAfter: 2, w: bufB}
chA := ws.Add(bufA)
chB := ws.Add(failB)
chC := ws.Add(bufC)
n, err := fmt.Fprint(&ws, "123")
assert.Equal(t, 3, n)
assert.NoError(t, err)
assert.Equal(t, "123", bufA.String())
assert.Equal(t, "12", bufB.String())
assert.Equal(t, "123", bufC.String())
assert.True(t, ws.Contains(bufC))
ws.Remove(bufC)
assert.False(t, ws.Contains(bufC))
// a should still be open
errA, isClosedA := checkErrChan(chA)
assert.NoError(t, errA)
assert.False(t, isClosedA)
// b should be closed with an error
errB, isClosedB := checkErrChan(chB)
assert.Equal(t, errB, ErrPartialWrite{
Writer: failB,
Err: errFailWriterHitLimit,
Expected: 3,
Wrote: 2,
})
assert.True(t, isClosedB)
// c should be closed with no error
errC, isClosedC := checkErrChan(chC)
assert.NoError(t, errC)
assert.True(t, isClosedC, chC)
}
func checkErrChan(ch <-chan error) (err error, isClosed bool) {
var isOK bool
select {
case err, isOK = <-ch:
if !isOK {
isClosed = true
} else {
_, isClosed = checkErrChan(ch)
}
default:
}
return
}
var errFailWriterHitLimit = errors.New("failing to write beyond limit")
type failWriter struct {
written int
failAfter int
w io.Writer
}
func (fw *failWriter) Write(b []byte) (int, error) {
writtenAfterWrite := fw.written + len(b)
doFail := false // used to identify the case where we are hitting the limit
if writtenAfterWrite > fw.failAfter {
tooFar := writtenAfterWrite - fw.failAfter
doFail = true
b = b[:len(b)-tooFar]
}
n, err := fw.w.Write(b)
if err != nil {
return n, err
}
fw.written += n
if doFail {
return n, errFailWriterHitLimit
}
return n, nil
}