diff --git a/update_attempter_unittest.cc b/update_attempter_unittest.cc
index 4ebc85c..911f664 100644
--- a/update_attempter_unittest.cc
+++ b/update_attempter_unittest.cc
@@ -48,6 +48,7 @@
 #include "update_engine/fake_system_state.h"
 #include "update_engine/mock_p2p_manager.h"
 #include "update_engine/mock_payload_state.h"
+#include "update_engine/mock_service_observer.h"
 #include "update_engine/payload_consumer/filesystem_verifier_action.h"
 #include "update_engine/payload_consumer/install_plan.h"
 #include "update_engine/payload_consumer/payload_constants.h"
@@ -219,6 +220,7 @@
   EXPECT_CALL(*prefs_, GetInt64(kPrefsDeltaUpdateFailures, _)).Times(0);
   attempter_.ActionCompleted(nullptr, &action, ErrorCode::kSuccess);
   EXPECT_EQ(UpdateStatus::FINALIZING, attempter_.status());
+  EXPECT_EQ(0.0, attempter_.download_progress_);
   ASSERT_EQ(nullptr, attempter_.error_event_.get());
 }
 
@@ -232,6 +234,79 @@
   ASSERT_NE(nullptr, attempter_.error_event_.get());
 }
 
+TEST_F(UpdateAttempterTest, DownloadProgressAccumulationTest) {
+  // Simple test case, where all the values match (nothing was skipped)
+  uint64_t bytes_progressed_1 = 1024 * 1024;  // 1MB
+  uint64_t bytes_progressed_2 = 1024 * 1024;  // 1MB
+  uint64_t bytes_received_1 = bytes_progressed_1;
+  uint64_t bytes_received_2 = bytes_received_1 + bytes_progressed_2;
+  uint64_t bytes_total = 20 * 1024 * 1024;  // 20MB
+
+  double progress_1 =
+      static_cast<double>(bytes_received_1) / static_cast<double>(bytes_total);
+  double progress_2 =
+      static_cast<double>(bytes_received_2) / static_cast<double>(bytes_total);
+
+  EXPECT_EQ(0.0, attempter_.download_progress_);
+  // This is set via inspecting the InstallPlan payloads when the
+  // OmahaResponseAction is completed
+  attempter_.new_payload_size_ = bytes_total;
+  NiceMock<MockServiceObserver> observer;
+  EXPECT_CALL(observer,
+              SendStatusUpdate(
+                  _, progress_1, UpdateStatus::DOWNLOADING, _, bytes_total));
+  EXPECT_CALL(observer,
+              SendStatusUpdate(
+                  _, progress_2, UpdateStatus::DOWNLOADING, _, bytes_total));
+  attempter_.AddObserver(&observer);
+  attempter_.BytesReceived(bytes_progressed_1, bytes_received_1, bytes_total);
+  EXPECT_EQ(progress_1, attempter_.download_progress_);
+  // This iteration validates that a later set of updates to the variables are
+  // properly handled (so that |getStatus()| will return the same progress info
+  // as the callback is receiving.
+  attempter_.BytesReceived(bytes_progressed_2, bytes_received_2, bytes_total);
+  EXPECT_EQ(progress_2, attempter_.download_progress_);
+}
+
+TEST_F(UpdateAttempterTest, ChangeToDownloadingOnReceivedBytesTest) {
+  // The transition into UpdateStatus::DOWNLOADING happens when the
+  // first bytes are received.
+  uint64_t bytes_progressed = 1024 * 1024;    // 1MB
+  uint64_t bytes_received = 2 * 1024 * 1024;  // 2MB
+  uint64_t bytes_total = 20 * 1024 * 1024;    // 300MB
+  attempter_.status_ = UpdateStatus::CHECKING_FOR_UPDATE;
+  // This is set via inspecting the InstallPlan payloads when the
+  // OmahaResponseAction is completed
+  attempter_.new_payload_size_ = bytes_total;
+  EXPECT_EQ(0.0, attempter_.download_progress_);
+  NiceMock<MockServiceObserver> observer;
+  EXPECT_CALL(
+      observer,
+      SendStatusUpdate(_, _, UpdateStatus::DOWNLOADING, _, bytes_total));
+  attempter_.AddObserver(&observer);
+  attempter_.BytesReceived(bytes_progressed, bytes_received, bytes_total);
+  EXPECT_EQ(UpdateStatus::DOWNLOADING, attempter_.status_);
+}
+
+TEST_F(UpdateAttempterTest, BroadcastCompleteDownloadTest) {
+  // There is a special case to ensure that at 100% downloaded,
+  // download_progress_ is updated and that value broadcast. This test confirms
+  // that.
+  uint64_t bytes_progressed = 0;              // ignored
+  uint64_t bytes_received = 5 * 1024 * 1024;  // ignored
+  uint64_t bytes_total = 5 * 1024 * 1024;     // 300MB
+  attempter_.status_ = UpdateStatus::DOWNLOADING;
+  attempter_.new_payload_size_ = bytes_total;
+  EXPECT_EQ(0.0, attempter_.download_progress_);
+  NiceMock<MockServiceObserver> observer;
+  EXPECT_CALL(
+      observer,
+      SendStatusUpdate(_, 1.0, UpdateStatus::DOWNLOADING, _, bytes_total));
+  attempter_.AddObserver(&observer);
+  attempter_.BytesReceived(bytes_progressed, bytes_received, bytes_total);
+  EXPECT_EQ(1.0, attempter_.download_progress_);
+}
+
 TEST_F(UpdateAttempterTest, ActionCompletedOmahaRequestTest) {
   unique_ptr<MockHttpFetcher> fetcher(new MockHttpFetcher("", 0, nullptr));
   fetcher->FailTransfer(500);  // Sets the HTTP response code.