1 files changed, 13 insertions, 0 deletions
diff --git a/libgo/go/flag/flag_test.go b/libgo/go/flag/flag_test.go
index 698c15f2c58..a9561f269f9 100644
--- a/libgo/go/flag/flag_test.go
+++ b/libgo/go/flag/flag_test.go
@@ -5,10 +5,12 @@
 package flag_test
 
 import (
+	"bytes"
 	. "flag"
 	"fmt"
 	"os"
 	"sort"
+	"strings"
 	"testing"
 	"time"
 )
@@ -206,6 +208,17 @@ func TestUserDefined(t *testing.T) {
 	}
 }
 
+func TestSetOutput(t *testing.T) {
+	var flags FlagSet
+	var buf bytes.Buffer
+	flags.SetOutput(&buf)
+	flags.Init("test", ContinueOnError)
+	flags.Parse([]string{"-unknown"})
+	if out := buf.String(); !strings.Contains(out, "-unknown") {
+		t.Logf("expected output mentioning unknown; got %q", out)
+	}
+}
+
 // This tests that one can reset the flags. This still works but not well, and is
 // superseded by FlagSet.
 func TestChangingArgs(t *testing.T) {