wal: add a test for wal cleanup, improve comments

To add test coverage of wal cleanup.

wal/wal.go

@@ -234,9 +234,9 @@ func (w *WAL) cleanupWAL(lg *zap.Logger) {
 	var err error
 	if err = w.Close(); err != nil {
 		if lg != nil {
-			lg.Panic("failed to closeup WAL during cleanup", zap.Error(err))
+			lg.Panic("failed to close WAL during cleanup", zap.Error(err))
 		} else {
-			plog.Panicf("failed to closeup WAL during cleanup: %v", err)
+			plog.Panicf("failed to close WAL during cleanup: %v", err)
 		}
 	}
 	brokenDirName := fmt.Sprintf("%s.broken.%v", w.dir, time.Now().Format("20060102.150405.999999"))

wal/wal_test.go

@@ -16,13 +16,15 @@ package wal
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"math"
 	"os"
 	"path"
 	"path/filepath"
 	"reflect"
+	"regexp"
 	"testing"
 
 	"go.etcd.io/etcd/v3/pkg/fileutil"
@@ -101,6 +103,37 @@ func TestCreateFailFromPollutedDir(t *testing.T) {
 	}
 }
 
+func TestWalCleanup(t *testing.T) {
+	testRoot, err := ioutil.TempDir(os.TempDir(), "waltestroot")
+	if err != nil {
+		t.Fatal(err)
+	}
+	p, err := ioutil.TempDir(testRoot, "waltest")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(testRoot)
+
+	logger := zap.NewExample()
+	w, err := Create(logger, p, []byte(""))
+	if err != nil {
+		t.Fatalf("err = %v, want nil", err)
+	}
+	w.cleanupWAL(logger)
+	fnames, err := fileutil.ReadDir(testRoot)
+	if err != nil {
+		t.Fatalf("err = %v, want nil", err)
+	}
+	if len(fnames) != 1 {
+		t.Fatalf("expected 1 file under %v, got %v", testRoot, len(fnames))
+	}
+	pattern := fmt.Sprintf(`%s.broken\.[\d]{8}\.[\d]{6}\.[\d]{6}`, filepath.Base(p))
+	match, _ := regexp.MatchString(pattern, fnames[0])
+	if !match {
+		t.Fatalf("match = false, expected true for %v with pattern %v", fnames[0], pattern)
+	}
+}
+
 func TestCreateFailFromNoSpaceLeft(t *testing.T) {
 	p, err := ioutil.TempDir(os.TempDir(), "waltest")
 	if err != nil {