Merge pull request #16444 from fgimenez/11584-pkg-stdcopy-test-coverage

Added tests for Write

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)