testing: fix build

Dependency on bufio crept in during last CL; this breaks the cycle.
Also add a missing '-' to the documentation.

R=rsc
CC=golang-dev
https://golang.org/cl/4274061

src/cmd/gotest/doc.go

@@ -42,7 +42,7 @@ The resulting binary, called (for amd64) 6.out, has several flags.
 
 Usage:
 	6.out [-test.v] [-test.run pattern] [-test.bench pattern] \
-		[test.memprofile=prof.out] [-test.memprofilerate=1]
+		[-test.memprofile=prof.out] [-test.memprofilerate=1]
 
 The -test.v flag causes the tests to be logged as they run.  The
 -test.run flag causes only those tests whose names match the regular

src/pkg/bufio/bufio_test.go

@@ -2,9 +2,10 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package bufio
+package bufio_test
 
 import (
+	. "bufio"
 	"bytes"
 	"fmt"
 	"io"
@@ -502,9 +503,8 @@ func TestWriteString(t *testing.T) {
 	b.WriteString("7890")                      // easy after flush
 	b.WriteString("abcdefghijklmnopqrstuvwxy") // hard
 	b.WriteString("z")
-	b.Flush()
-	if b.err != nil {
-		t.Error("WriteString", b.err)
+	if err := b.Flush(); err != nil {
+		t.Error("WriteString", err)
 	}
 	s := "01234567890abcdefghijklmnopqrstuvwxyz"
 	if string(buf.Bytes()) != s {