Add internal package for testing

internal/Makefile

@@ -0,0 +1,2 @@
+all:
+	gotest -v -benchmem -run=.* -bench=.* .

internal/internal_test.go

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+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+package internal
+
+import (
+	"testing"
+	"time"
+)
+
+func TestA(t *testing.T) {
+}
+
+func TestB(t *testing.T) {
+	t.Fatal("failed")
+}
+
+func TestC(t *testing.T) {
+	t.Parallel()
+	time.Sleep(time.Second)
+	t.Fatal("failed")
+}
+
+func TestD(t *testing.T) {
+	t.Parallel()
+	t.Fatal("failed")
+}
+
+func BenchmarkA(b *testing.B) {
+}