diff --git a/dbus_wrapper_interface.h b/dbus_wrapper_interface.h
new file mode 100644
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--- /dev/null
+++ b/dbus_wrapper_interface.h
@@ -0,0 +1,92 @@
+// Copyright (c) 2010 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.
+
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_WRAPPER_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_WRAPPER_H_
+
+// A mockable interface for DBus.
+
+#include <dbus/dbus-glib.h>
+#include <dbus/dbus.h>
+
+#ifndef DBUS_TYPE_G_OBJECT_PATH_ARRAY
+#define DBUS_TYPE_G_OBJECT_PATH_ARRAY \
+  (dbus_g_type_get_collection ("GPtrArray", DBUS_TYPE_G_OBJECT_PATH))
+#endif
+
+#ifndef DBUS_TYPE_G_STRING_ARRAY
+#define DBUS_TYPE_G_STRING_ARRAY \
+  (dbus_g_type_get_collection ("GPtrArray", G_TYPE_STRING))
+#endif
+
+namespace chromeos_update_engine {
+
+class DBusWrapperInterface {
+ public:
+  // Wraps dbus_g_proxy_new_for_name().
+  virtual DBusGProxy* ProxyNewForName(DBusGConnection* connection,
+                                      const char* name,
+                                      const char* path,
+                                      const char* interface) = 0;
+
+  // Wraps g_object_unref().
+  virtual void ProxyUnref(DBusGProxy* proxy) = 0;
+
+  // Wraps dbus_g_bus_get().
+  virtual DBusGConnection* BusGet(DBusBusType type, GError** error) = 0;
+
+  // Wraps dbus_g_proxy_call(). Since this is a variadic function without a
+  // va_list equivalent, we have to list specific wrappers depending on the
+  // number of input and output arguments, based on the required usage. Note,
+  // however, that we do rely on automatic signature overriding to facilitate
+  // different types of input/output arguments.
+  virtual gboolean ProxyCall_0_1(DBusGProxy* proxy,
+                                 const char* method,
+                                 GError** error,
+                                 GHashTable** out1) = 0;
+
+  virtual gboolean ProxyCall_3_0(DBusGProxy* proxy,
+                                 const char* method,
+                                 GError** error,
+                                 const char* in1,
+                                 const char* in2,
+                                 const char* in3) = 0;
+
+  // Wraps dbus_g_connection_get_connection().
+  virtual DBusConnection* ConnectionGetConnection(DBusGConnection* gbus) = 0;
+
+  // Wraps dbus_bus_add_match().
+  virtual void DBusBusAddMatch(DBusConnection* connection,
+                               const char* rule,
+                               DBusError* error) = 0;
+
+  // Wraps dbus_connection_add_filter().
+  virtual dbus_bool_t DBusConnectionAddFilter(
+      DBusConnection* connection,
+      DBusHandleMessageFunction function,
+      void* user_data,
+      DBusFreeFunction free_data_function) = 0;
+
+  // Wraps dbus_connection_remove_filter().
+  virtual void DBusConnectionRemoveFilter(DBusConnection* connection,
+                                          DBusHandleMessageFunction function,
+                                          void* user_data) = 0;
+
+  // Wraps dbus_message_is_signal().
+  virtual dbus_bool_t DBusMessageIsSignal(DBusMessage* message,
+                                          const char* interface,
+                                          const char* signal_name) = 0;
+
+  // Wraps dbus_message_get_args(). Deploys the same approach for handling
+  // variadic arguments as ProxyCall above.
+  virtual dbus_bool_t DBusMessageGetArgs_3(DBusMessage* message,
+                                           DBusError* error,
+                                           char** out1,
+                                           char** out2,
+                                           char** out3) = 0;
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_WRAPPER_H_