Add stderr vs stdout test

Author: cmoog

localexec.go

@@ -134,6 +134,6 @@ func (w disabledStdinWriter) Close() error {
 	return nil
 }
 
-func (w disabledStdinWriter) Write(a []byte) (written int, err error) {
+func (w disabledStdinWriter) Write(_ []byte) (written int, err error) {
 	return 0, xerrors.Errorf("stdin is not enabled for this command")
 }

localexec_test.go

@@ -1,6 +1,7 @@
 package wsep
 
 import (
+	"bytes"
 	"context"
 	"io"
 	"io/ioutil"
@@ -117,3 +118,32 @@ func TestStdinFail(t *testing.T) {
 	err = process.Wait()
 	assert.Success(t, "process wait", err)
 }
+
+func TestStdoutVsStderr(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	var (
+		execer LocalExecer
+		stdout bytes.Buffer
+		stderr bytes.Buffer
+	)
+	process, err := execer.Start(ctx, Command{
+		Command: "sh",
+		Args: []string{"-c", "echo stdout-message; echo 1>&2 stderr-message"},
+		Stdin: false,
+		TTY: false,
+	})
+	assert.Success(t, "start command", err)
+
+	go io.Copy(&stdout, process.Stdout())
+	go io.Copy(&stderr, process.Stderr())
+
+	time.Sleep(time.Second)
+	err = process.Wait()
+	assert.Success(t, "wait for process to complete", err)
+
+	assert.Equal(t, "stdout", "stdout-message", strings.TrimSpace(stdout.String()))
+	assert.Equal(t, "stderr", "stderr-message", strings.TrimSpace(stderr.String()))
+}
+