SimpleShellReader prints a newline when it reads EOF

shell.go

@@ -64,6 +64,7 @@ type ShellReader interface {
 type SimpleShellReader struct {
 	r      io.Reader
 	br     *bufio.Reader
+	out    io.Writer
 	prompt string
 }
 
@@ -72,15 +73,34 @@ func NewShellReader(r io.Reader, prompt string) *SimpleShellReader {
 		r = os.Stdin
 	}
 	br := bufio.NewReader(r)
-	return &SimpleShellReader{r, br, prompt}
+	return &SimpleShellReader{r, br, os.Stdout, prompt}
+}
+
+func (s *SimpleShellReader) SetOutput(w io.Writer) {
+	s.out = w
+}
+
+func (s *SimpleShellReader) print(v ...interface{}) {
+	if s.out != nil {
+		fmt.Fprint(s.out, v...)
+	}
+}
+
+func (s *SimpleShellReader) println(v ...interface{}) {
+	if s.out != nil {
+		fmt.Fprintln(s.out, v...)
+	}
 }
 
 func (s *SimpleShellReader) ReadCommand() (cmd []string, eof bool, err error) {
-	fmt.Print(s.prompt)
+	s.print(s.prompt)
 	bs, err := s.br.ReadBytes('\n')
 	eof = err == io.EOF
+	if eof {
+		s.println()
+	}
 	if err != nil {
-		if err == io.EOF && len(bs) > 0 {
+		if eof && len(bs) > 0 {
 			// this is ok
 		} else {
 			return nil, eof, err

shell_test.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"io"
+	"io/ioutil"
 	"reflect"
 	"strings"
 	"testing"
@@ -15,6 +16,7 @@ func StringShellReader(lines string) *SimpleShellReader {
 
 func TestShellReaderReadCommand_eof(t *testing.T) {
 	sh := StringShellReader("")
+	sh.SetOutput(ioutil.Discard)
 	_, eof, err := sh.ReadCommand()
 	if err != io.EOF {
 		t.Fatal("non-eof error returned")
@@ -24,6 +26,7 @@ func TestShellReaderReadCommand_eof(t *testing.T) {
 	}
 
 	sh = StringShellReader(":hello shell")
+	sh.SetOutput(ioutil.Discard)
 	_, eof, err = sh.ReadCommand()
 	if err != nil {
 		t.Fatal("error returned")
@@ -35,6 +38,7 @@ func TestShellReaderReadCommand_eof(t *testing.T) {
 
 func TestShellReaderReadCommand_multi(t *testing.T) {
 	sh := StringShellReader(":hello\n:shell\n")
+	sh.SetOutput(ioutil.Discard)
 	cmd, eof, err := sh.ReadCommand()
 	if err != nil {
 		t.Fatalf("error returned")
@@ -81,7 +85,9 @@ func TestShellReaderReadCommand_single(t *testing.T) {
 		{".items | .[]", cmd("push", ".items | .[]")},
 		{"\n", cmd("write")},
 	} {
-		cmd, _, err := StringShellReader(test.str).ReadCommand()
+		sh := StringShellReader(test.str)
+		sh.SetOutput(ioutil.Discard)
+		cmd, _, err := sh.ReadCommand()
 		if err != nil {
 			t.Errorf("command %d (%q) %v", i, test.str, err)
 			continue