[battor agent] Move code for stringifying bytes into a util file

tools/battor_agent/serial_utils_unittest.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "tools/battor_agent/serial_utils.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+using namespace testing;
+
+namespace battor {
+
+TEST(SerialUtilsTest, CharVectorToStringLengthZero) {
+  EXPECT_EQ("", CharVectorToString(std::vector<char>()));
+}
+
+TEST(SerialUtilsTest, CharVectorToStringLengthOne) {
+  EXPECT_EQ("0x41", CharVectorToString(std::vector<char>({'A'})));
+}
+
+TEST(SerialUtilsTest, CharVectorToStringLengthTwo) {
+  EXPECT_EQ("0x41 0x4a",
+            CharVectorToString(std::vector<char>({'A', 'J'})));
+}
+
+TEST(SerialUtilsTest, CharArrayToStringLengthOne) {
+  const char arr[] = {'A'};
+  EXPECT_EQ("0x41", CharArrayToString(arr, sizeof(arr)));
+}
+
+TEST(SerialUtilsTest, CharArrayToStringLengthTwo) {
+  const char arr[] = {'A', 'J'};
+  EXPECT_EQ("0x41 0x4a", CharArrayToString(arr, sizeof(arr)));
+}
+
+}  // namespace battor