diff --git a/fake_hardware.cc b/fake_hardware.cc
new file mode 100644
index 0000000..604358d
--- /dev/null
+++ b/fake_hardware.cc
@@ -0,0 +1,24 @@
+// Copyright (c) 2013 The Chromium OS 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 "update_engine/fake_hardware.h"
+
+using std::string;
+
+namespace chromeos_update_engine {
+
+const string FakeHardware::KernelDeviceOfBootDevice(
+    const string& boot_device) {
+  KernelDevicesMap::iterator it = kernel_devices_.find(boot_device);
+  if (it == kernel_devices_.end())
+    return "";
+  return it->second;
+}
+
+void FakeHardware::SetKernelDeviceOfBootDevice(const string& boot_device,
+                                               const string& kernel_device) {
+  kernel_devices_[boot_device] = kernel_device;
+}
+
+}  // namespace chromeos_update_engine