diff --git a/update_attempter_unittest.cc b/update_attempter_unittest.cc
new file mode 100644
index 0000000..0a02d1c
--- /dev/null
+++ b/update_attempter_unittest.cc
@@ -0,0 +1,156 @@
+// 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.
+
+#include <base/file_util.h>
+#include <gtest/gtest.h>
+
+#include "update_engine/action_mock.h"
+#include "update_engine/action_processor_mock.h"
+#include "update_engine/filesystem_copier_action.h"
+#include "update_engine/postinstall_runner_action.h"
+#include "update_engine/set_bootable_flag_action.h"
+#include "update_engine/update_attempter.h"
+
+using std::string;
+using testing::InSequence;
+using testing::Property;
+using testing::Return;
+
+namespace chromeos_update_engine {
+
+// Test a subclass rather than the main class directly so that we can mock out
+// methods within the class. There're explicit unit test for the mocked out
+// methods.
+class UpdateAttempterUnderTest : public UpdateAttempter {
+ public:
+  UpdateAttempterUnderTest()
+      : UpdateAttempter(NULL, NULL) {}
+};
+
+class UpdateAttempterTest : public ::testing::Test {
+ protected:
+  virtual void SetUp() {
+    EXPECT_EQ(NULL, attempter_.dbus_service_);
+    EXPECT_EQ(NULL, attempter_.prefs_);
+    EXPECT_EQ(NULL, attempter_.metrics_lib_);
+    EXPECT_EQ(NULL, attempter_.update_check_scheduler_);
+    EXPECT_EQ(0, attempter_.http_response_code_);
+    EXPECT_EQ(utils::kProcessPriorityNormal, attempter_.priority_);
+    EXPECT_EQ(NULL, attempter_.manage_priority_source_);
+    EXPECT_FALSE(attempter_.download_active_);
+    EXPECT_EQ(UPDATE_STATUS_IDLE, attempter_.status_);
+    EXPECT_EQ(0.0, attempter_.download_progress_);
+    EXPECT_EQ(0, attempter_.last_checked_time_);
+    EXPECT_EQ("0.0.0.0", attempter_.new_version_);
+    EXPECT_EQ(0, attempter_.new_size_);
+    processor_ = new ActionProcessorMock();
+    attempter_.processor_.reset(processor_);  // Transfers ownership.
+  }
+
+  UpdateAttempterUnderTest attempter_;
+  ActionProcessorMock* processor_;
+};
+
+TEST_F(UpdateAttempterTest, ConstructWithUpdatedMarkerTest) {
+  extern const char* kUpdateCompletedMarker;
+  const FilePath kMarker(kUpdateCompletedMarker);
+  EXPECT_EQ(0, file_util::WriteFile(kMarker, "", 0));
+  UpdateAttempterUnderTest attempter;
+  EXPECT_EQ(UPDATE_STATUS_UPDATED_NEED_REBOOT, attempter.status());
+  EXPECT_TRUE(file_util::Delete(kMarker, false));
+}
+
+TEST_F(UpdateAttempterTest, GetErrorCodeForActionTest) {
+  extern ActionExitCode GetErrorCodeForAction(AbstractAction* action,
+                                              ActionExitCode code);
+  EXPECT_EQ(kActionCodeSuccess,
+            GetErrorCodeForAction(NULL, kActionCodeSuccess));
+
+  OmahaRequestParams params;
+  OmahaRequestAction omaha_request_action(NULL, params, NULL, NULL);
+  EXPECT_EQ(kActionCodeOmahaRequestError,
+            GetErrorCodeForAction(&omaha_request_action, kActionCodeError));
+  OmahaResponseHandlerAction omaha_response_handler_action;
+  EXPECT_EQ(kActionCodeOmahaResponseHandlerError,
+            GetErrorCodeForAction(&omaha_response_handler_action,
+                                  kActionCodeError));
+  FilesystemCopierAction filesystem_copier_action(false);
+  EXPECT_EQ(kActionCodeFilesystemCopierError,
+            GetErrorCodeForAction(&filesystem_copier_action, kActionCodeError));
+  PostinstallRunnerAction postinstall_runner_action(true);
+  EXPECT_EQ(kActionCodePostinstallRunnerError,
+            GetErrorCodeForAction(&postinstall_runner_action,
+                                  kActionCodeError));
+  SetBootableFlagAction set_bootable_flag_action;
+  EXPECT_EQ(kActionCodeSetBootableFlagError,
+            GetErrorCodeForAction(&set_bootable_flag_action,
+                                  kActionCodeError));
+  ActionMock action_mock;
+  EXPECT_CALL(action_mock, Type()).Times(1).WillOnce(Return("ActionMock"));
+  EXPECT_EQ(kActionCodeError,
+            GetErrorCodeForAction(&action_mock, kActionCodeError));
+}
+
+TEST_F(UpdateAttempterTest, UpdateStatusToStringTest) {
+  extern const char* UpdateStatusToString(UpdateStatus);
+  EXPECT_STREQ("UPDATE_STATUS_IDLE", UpdateStatusToString(UPDATE_STATUS_IDLE));
+  EXPECT_STREQ("UPDATE_STATUS_CHECKING_FOR_UPDATE",
+               UpdateStatusToString(UPDATE_STATUS_CHECKING_FOR_UPDATE));
+  EXPECT_STREQ("UPDATE_STATUS_UPDATE_AVAILABLE",
+               UpdateStatusToString(UPDATE_STATUS_UPDATE_AVAILABLE));
+  EXPECT_STREQ("UPDATE_STATUS_DOWNLOADING",
+               UpdateStatusToString(UPDATE_STATUS_DOWNLOADING));
+  EXPECT_STREQ("UPDATE_STATUS_VERIFYING",
+               UpdateStatusToString(UPDATE_STATUS_VERIFYING));
+  EXPECT_STREQ("UPDATE_STATUS_FINALIZING",
+               UpdateStatusToString(UPDATE_STATUS_FINALIZING));
+  EXPECT_STREQ("UPDATE_STATUS_UPDATED_NEED_REBOOT",
+               UpdateStatusToString(UPDATE_STATUS_UPDATED_NEED_REBOOT));
+  EXPECT_STREQ("UPDATE_STATUS_REPORTING_ERROR_EVENT",
+               UpdateStatusToString(UPDATE_STATUS_REPORTING_ERROR_EVENT));
+  EXPECT_STREQ("unknown status",
+               UpdateStatusToString(static_cast<UpdateStatus>(-1)));
+}
+
+TEST_F(UpdateAttempterTest, UpdateTest) {
+  attempter_.set_http_response_code(200);
+  InSequence s;
+  const string kActionTypes[] = {
+    OmahaRequestAction::StaticType(),
+    OmahaResponseHandlerAction::StaticType(),
+    FilesystemCopierAction::StaticType(),
+    FilesystemCopierAction::StaticType(),
+    OmahaRequestAction::StaticType(),
+    DownloadAction::StaticType(),
+    OmahaRequestAction::StaticType(),
+    PostinstallRunnerAction::StaticType(),
+    SetBootableFlagAction::StaticType(),
+    PostinstallRunnerAction::StaticType(),
+    OmahaRequestAction::StaticType()
+  };
+  for (size_t i = 0; i < arraysize(kActionTypes); ++i) {
+    EXPECT_CALL(*processor_,
+                EnqueueAction(Property(&AbstractAction::Type,
+                                       kActionTypes[i]))).Times(1);
+  }
+  EXPECT_CALL(*processor_, StartProcessing()).Times(1);
+
+  attempter_.Update("", "");
+
+  EXPECT_EQ(0, attempter_.http_response_code());
+  EXPECT_EQ(&attempter_, processor_->delegate());
+  EXPECT_EQ(arraysize(kActionTypes), attempter_.actions_.size());
+  for (size_t i = 0; i < arraysize(kActionTypes); ++i) {
+    EXPECT_EQ(kActionTypes[i], attempter_.actions_[i]->Type());
+  }
+  EXPECT_EQ(attempter_.response_handler_action_.get(),
+            attempter_.actions_[1].get());
+  DownloadAction* download_action =
+      dynamic_cast<DownloadAction*>(attempter_.actions_[5].get());
+  ASSERT_TRUE(download_action != NULL);
+  EXPECT_EQ(&attempter_, download_action->delegate());
+  EXPECT_EQ(UPDATE_STATUS_CHECKING_FOR_UPDATE, attempter_.status());
+}
+
+}  // namespace chromeos_update_engine