diff --git a/cmd/javac_wrapper/javac_wrapper.go b/cmd/javac_wrapper/javac_wrapper.go
index a323473..ab4d23f 100644
--- a/cmd/javac_wrapper/javac_wrapper.go
+++ b/cmd/javac_wrapper/javac_wrapper.go
@@ -47,14 +47,14 @@
 )
 
 func main() {
-	exitCode, err := Main(os.Args[0], os.Args[1:])
+	exitCode, err := Main(os.Stdout, os.Args[0], os.Args[1:])
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err.Error())
 	}
 	os.Exit(exitCode)
 }
 
-func Main(name string, args []string) (int, error) {
+func Main(out io.Writer, name string, args []string) (int, error) {
 	if len(args) < 1 {
 		return 1, fmt.Errorf("usage: %s javac ...", name)
 	}
@@ -78,7 +78,7 @@
 	// Process subprocess stdout asynchronously
 	errCh := make(chan error)
 	go func() {
-		errCh <- process(pr, os.Stdout)
+		errCh <- process(pr, out)
 	}()
 
 	// Wait for subprocess to finish
diff --git a/cmd/javac_wrapper/javac_wrapper_test.go b/cmd/javac_wrapper/javac_wrapper_test.go
index 9f41078..c345479 100644
--- a/cmd/javac_wrapper/javac_wrapper_test.go
+++ b/cmd/javac_wrapper/javac_wrapper_test.go
@@ -16,6 +16,7 @@
 
 import (
 	"bytes"
+	"io/ioutil"
 	"strconv"
 	"testing"
 )
@@ -82,7 +83,7 @@
 
 func TestSubprocess(t *testing.T) {
 	t.Run("failure", func(t *testing.T) {
-		exitCode, err := Main("test", []string{"sh", "-c", "exit 9"})
+		exitCode, err := Main(ioutil.Discard, "test", []string{"sh", "-c", "exit 9"})
 		if err != nil {
 			t.Fatal("unexpected error", err)
 		}
@@ -92,7 +93,7 @@
 	})
 
 	t.Run("signal", func(t *testing.T) {
-		exitCode, err := Main("test", []string{"sh", "-c", "kill -9 $$"})
+		exitCode, err := Main(ioutil.Discard, "test", []string{"sh", "-c", "kill -9 $$"})
 		if err != nil {
 			t.Fatal("unexpected error", err)
 		}
@@ -102,7 +103,7 @@
 	})
 
 	t.Run("success", func(t *testing.T) {
-		exitCode, err := Main("test", []string{"echo"})
+		exitCode, err := Main(ioutil.Discard, "test", []string{"echo"})
 		if err != nil {
 			t.Fatal("unexpected error", err)
 		}