Created an interface for DownloadFile, for use in unit tests.

content/browser/download/mock_download_file.h

Index: content/browser/download/mock_download_file.h
diff --git a/content/browser/download/mock_download_file.h b/content/browser/download/mock_download_file.h
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+++ b/content/browser/download/mock_download_file.h
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+// Copyright (c) 2011 The Chromium 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 CONTENT_BROWSER_DOWNLOAD_MOCK_DOWNLOAD_FILE_H_
+#define CONTENT_BROWSER_DOWNLOAD_MOCK_DOWNLOAD_FILE_H_
+#pragma once
+
+#include <string>
+#include <map>
+
+#include "base/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "content/browser/download/download_file.h"
+#include "content/browser/download/download_id.h"
+#include "content/browser/download/download_manager.h"
+#include "content/browser/download/download_request_handle.h"
+#include "net/base/net_errors.h"
+
+struct DownloadCreateInfo;
+
+class MockDownloadFile : virtual public DownloadFile {

[Randy Smith (Not in Mondays), 2011/11/14 21:58:39]

What are the advantages of creating this class as opposed to using a GMock? 
(I'm not sure, which is why I ask :-}, but if you can get the same functionality
with a gmock, that's probably easier for people who are familiar with gmocks to
understand.)

[ahendrickson, 2011/11/16 19:39:11]

It's a lot more flexible.  You can monitor stuff, inject errors, whatever you
want.

At the moment it's only mimicking what GMock did, but that will change.

+ public:
+  // Class to extract statistics from the usage of |MockDownloadFile|.
+  class StatisticsRecorder {
+   public:
+    enum StatisticsIndex {
+      STAT_INITIALIZE,
+      STAT_APPEND,
+      STAT_RENAME,
+      STAT_DETACH,
+      STAT_CANCEL,
+      STAT_FINISH,
+      STAT_BYTES
+    };
+
+    StatisticsRecorder();
+    ~StatisticsRecorder();
+
+    // Records the statistic.
+    // |index| indicates what statistic to use.
+    void Record(StatisticsIndex index);
+
+    // Adds to the statistic.
+    // |index| indicates what statistic to use.
+    void Add(StatisticsIndex index, int count);
+
+    // Returns the statistic value.
+    // |index| indicates what statistic to use.
+    int Count(StatisticsIndex index);
+
+   private:
+    typedef std::map<StatisticsIndex, int> StatisticsMap;
+
+    StatisticsMap map_;
+  };
+
+  MockDownloadFile(const DownloadCreateInfo* info,
+                   const DownloadRequestHandle& request_handle,
+                   DownloadManager* download_manager,
+                   StatisticsRecorder* recorder);
+  virtual ~MockDownloadFile();
+
+  // DownloadFile functions.
+  virtual net::Error Initialize(bool calculate_hash) OVERRIDE;
+  virtual net::Error AppendDataToFile(const char* data,
+                                      size_t data_len) OVERRIDE;
+  virtual net::Error Rename(const FilePath& full_path) OVERRIDE;
+  virtual void Detach() OVERRIDE;
+  virtual void Cancel() OVERRIDE;
+  virtual void Finish() OVERRIDE;
+  virtual void AnnotateWithSourceInformation() OVERRIDE;
+  virtual FilePath FullPath() const OVERRIDE;
+  virtual bool InProgress() const OVERRIDE;
+  virtual int64 BytesSoFar() const OVERRIDE;
+  virtual bool GetSha256Hash(std::string* hash) OVERRIDE;
+  virtual void CancelDownloadRequest() OVERRIDE;
+  virtual int Id() const OVERRIDE;
+  virtual DownloadManager* GetDownloadManager() OVERRIDE;
+  virtual const DownloadId& GlobalId() const OVERRIDE;
+  virtual std::string DebugString() const OVERRIDE;
+
+  // Functions relating to setting and checking expectations.
+  size_t rename_count() const { return rename_count_; }
+  void SetExpectedPath(size_t index, const FilePath& path);
+
+ private:
+  // The unique identifier for this download, assigned at creation by
+  // the DownloadFileManager for its internal record keeping.
+  DownloadId id_;
+
+  // The handle to the request information.  Used for operations outside the
+  // download system, specifically canceling a download.
+  DownloadRequestHandle request_handle_;
+
+  // DownloadManager this download belongs to.
+  scoped_refptr<DownloadManager> download_manager_;
+
+  // Records usage statistics.  Not owned by this class (survives destruction).
+  StatisticsRecorder* recorder_;
+
+  // The number of times |Rename()| has been called.
+  // Used instead of checking |recorder_| because the latter can be NULL.
+  size_t rename_count_;
+
+  // A vector of paths that we expect to call |Rename()| with.
+  std::vector<FilePath> expected_rename_path_list_;
+
+  // A buffer to hold the data we write.
+  std::string data_;
+
+  // Dummy in-progress flag.
+  bool in_progress_;
+};
+
+#endif  // CONTENT_BROWSER_DOWNLOAD_MOCK_DOWNLOAD_FILE_H_