diff --git a/mock_http_fetcher.cc b/mock_http_fetcher.cc
new file mode 100644
index 0000000..0c4209a
--- /dev/null
+++ b/mock_http_fetcher.cc
@@ -0,0 +1,99 @@
+// Copyright (c) 2009 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 "glog/logging.h"
+#include "update_engine/mock_http_fetcher.h"
+
+// This is a mac implementation of HttpFetcher which is useful for testing.
+
+namespace chromeos_update_engine {
+
+MockHttpFetcher::~MockHttpFetcher() {
+  CHECK(!timeout_source_) << "Call TerminateTransfer() before dtor.";
+}
+
+void MockHttpFetcher::BeginTransfer(const std::string& url) {
+  if (sent_size_ < data_.size())
+    SendData(true);
+}
+
+// Returns false on one condition: If timeout_source_ was already set
+// and it needs to be deleted by the caller. If timeout_source_ is NULL
+// when this function is called, this function will always return true.
+bool MockHttpFetcher::SendData(bool skip_delivery) {
+  CHECK_LT(sent_size_, data_.size());
+  if (!skip_delivery) {
+    const size_t chunk_size = min(kMockHttpFetcherChunkSize,
+                                  data_.size() - sent_size_);
+    CHECK(delegate_);
+    delegate_->ReceivedBytes(this, &data_[sent_size_], chunk_size);
+    sent_size_ += chunk_size;
+    CHECK_LE(sent_size_, data_.size());
+    if (sent_size_ == data_.size()) {
+      // We've sent all the data. notify of success
+      delegate_->TransferComplete(this, true);
+    }
+  }
+
+  if (paused_) {
+    // If we're paused, we should return true if timeout_source_ is set,
+    // since we need the caller to delete it.
+    return timeout_source_;
+  }
+
+  if (timeout_source_) {
+    // we still need a timeout if there's more data to send
+    return sent_size_ < data_.size();
+  } else if (sent_size_ < data_.size()) {
+    // we don't have a timeout source and we need one
+    timeout_source_ = g_timeout_source_new(10);
+    CHECK(timeout_source_);
+    g_source_set_callback(timeout_source_, StaticTimeoutCallback, this,
+                          NULL);
+    timout_tag_ = g_source_attach(timeout_source_, NULL);
+  }
+  return true;
+}
+
+bool MockHttpFetcher::TimeoutCallback() {
+  CHECK(!paused_);
+  bool ret = SendData(false);
+  if (false == ret) {
+    timeout_source_ = NULL;
+  }
+  return ret;
+}
+
+// If the transfer is in progress, aborts the transfer early.
+// The transfer cannot be resumed.
+void MockHttpFetcher::TerminateTransfer() {
+  sent_size_ = data_.size();
+  // kill any timeout
+  if (timeout_source_) {
+    g_source_remove(timout_tag_);
+    g_source_destroy(timeout_source_);
+    timeout_source_ = NULL;
+  }
+}
+
+void MockHttpFetcher::Pause() {
+  CHECK(!paused_);
+  paused_ = true;
+  if (timeout_source_) {
+    g_source_remove(timout_tag_);
+    g_source_destroy(timeout_source_);
+    timeout_source_ = NULL;
+  }
+
+}
+
+void MockHttpFetcher::Unpause() {
+  CHECK(paused_) << "You must pause before unpause.";
+  paused_ = false;
+  if (sent_size_ < data_.size()) {
+    SendData(false);
+  }
+}
+
+}  // namespace chromeos_update_engine