Add Serializer plugins, and 'file' output plugin

plugins/outputs/file/file_test.go

 package file
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/plugins/serializers"
+	"github.com/influxdata/telegraf/testutil"
+)
+
+const (
+	expNewFile   = "test1,tag1=value1 value=1 1257894000000000000\n"
+	expExistFile = "cpu,cpu=cpu0 value=100 1455312810012459582\n" +
+		"test1,tag1=value1 value=1 1257894000000000000\n"
+)
+
+func TestFileExistingFile(t *testing.T) {
+	fh := createFile()
+	s, _ := serializers.NewInfluxSerializer()
+	f := File{
+		Files:      []string{fh.Name()},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh.Name(), expExistFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileNewFile(t *testing.T) {
+	s, _ := serializers.NewInfluxSerializer()
+	fh := tmpFile()
+	f := File{
+		Files:      []string{fh},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh, expNewFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileExistingFiles(t *testing.T) {
+	fh1 := createFile()
+	fh2 := createFile()
+	fh3 := createFile()
+
+	s, _ := serializers.NewInfluxSerializer()
+	f := File{
+		Files:      []string{fh1.Name(), fh2.Name(), fh3.Name()},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh1.Name(), expExistFile, t)
+	validateFile(fh2.Name(), expExistFile, t)
+	validateFile(fh3.Name(), expExistFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileNewFiles(t *testing.T) {
+	s, _ := serializers.NewInfluxSerializer()
+	fh1 := tmpFile()
+	fh2 := tmpFile()
+	fh3 := tmpFile()
+	f := File{
+		Files:      []string{fh1, fh2, fh3},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh1, expNewFile, t)
+	validateFile(fh2, expNewFile, t)
+	validateFile(fh3, expNewFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileBoth(t *testing.T) {
+	fh1 := createFile()
+	fh2 := tmpFile()
+
+	s, _ := serializers.NewInfluxSerializer()
+	f := File{
+		Files:      []string{fh1.Name(), fh2},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh1.Name(), expExistFile, t)
+	validateFile(fh2, expNewFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileStdout(t *testing.T) {
+	// keep backup of the real stdout
+	old := os.Stdout
+	r, w, _ := os.Pipe()
+	os.Stdout = w
+
+	s, _ := serializers.NewInfluxSerializer()
+	f := File{
+		Files:      []string{"stdout"},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	err = f.Close()
+	assert.NoError(t, err)
+
+	outC := make(chan string)
+	// copy the output in a separate goroutine so printing can't block indefinitely
+	go func() {
+		var buf bytes.Buffer
+		io.Copy(&buf, r)
+		outC <- buf.String()
+	}()
+
+	// back to normal state
+	w.Close()
+	// restoring the real stdout
+	os.Stdout = old
+	out := <-outC
+
+	assert.Equal(t, expNewFile, out)
+}
+
+func createFile() *os.File {
+	f, err := ioutil.TempFile("", "")
+	if err != nil {
+		panic(err)
+	}
+	f.WriteString("cpu,cpu=cpu0 value=100 1455312810012459582\n")
+	return f
+}
+
+func tmpFile() string {
+	d, err := ioutil.TempDir("", "")
+	if err != nil {
+		panic(err)
+	}
+	return d + internal.RandomString(10)
+}
+
+func validateFile(fname, expS string, t *testing.T) {
+	buf, err := ioutil.ReadFile(fname)
+	if err != nil {
+		panic(err)
+	}
+	assert.Equal(t, expS, string(buf))
+}