From 2ef06c2b5688be191ed3c112075d7cea30b30e5f Mon Sep 17 00:00:00 2001
From: Federico Gimenez <fgimenez@coit.es>
Date: Sun, 20 Sep 2015 11:46:53 +0200
Subject: [PATCH] Added tests for StdWriter.Write.

The tests added cover the case when the Writer field returns and error
and, related to that, when the number of written bytes is less than 0.

Signed-off-by: Federico Gimenez <fgimenez@coit.es>
---
 stdcopy/stdcopy_test.go | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/stdcopy/stdcopy_test.go b/stdcopy/stdcopy_test.go
index 7351ce0..c9964aa 100644
--- a/stdcopy/stdcopy_test.go
+++ b/stdcopy/stdcopy_test.go
@@ -2,6 +2,7 @@ package stdcopy
 
 import (
 	"bytes"
+	"errors"
 	"io/ioutil"
 	"strings"
 	"testing"
@@ -49,6 +50,41 @@ func TestWrite(t *testing.T) {
 	}
 }
 
+type errWriter struct {
+	n   int
+	err error
+}
+
+func (f *errWriter) Write(buf []byte) (int, error) {
+	return f.n, f.err
+}
+
+func TestWriteWithWriterError(t *testing.T) {
+	expectedError := errors.New("expected")
+	expectedReturnedBytes := 10
+	writer := NewStdWriter(&errWriter{
+		n:   stdWriterPrefixLen + expectedReturnedBytes,
+		err: expectedError}, Stdout)
+	data := []byte("This won't get written, sigh")
+	n, err := writer.Write(data)
+	if err != expectedError {
+		t.Fatalf("Didn't get expected error.")
+	}
+	if n != expectedReturnedBytes {
+		t.Fatalf("Didn't get expected writen bytes %d, got %d.",
+			expectedReturnedBytes, n)
+	}
+}
+
+func TestWriteDoesNotReturnNegativeWrittenBytes(t *testing.T) {
+	writer := NewStdWriter(&errWriter{n: -1}, Stdout)
+	data := []byte("This won't get written, sigh")
+	actual, _ := writer.Write(data)
+	if actual != 0 {
+		t.Fatalf("Expected returned written bytes equal to 0, got %d", actual)
+	}
+}
+
 func TestStdCopyWithInvalidInputHeader(t *testing.T) {
 	dstOut := NewStdWriter(ioutil.Discard, Stdout)
 	dstErr := NewStdWriter(ioutil.Discard, Stderr)