Clean up ARC file system unit tests.

components/arc/test/fake_file_system_instance.h

Index: components/arc/test/fake_file_system_instance.h
diff --git a/components/arc/test/fake_file_system_instance.h b/components/arc/test/fake_file_system_instance.h
index 98db1026d1f06eaad0925acc3c0ce5646898cae0..b530c26348edfff21ef9c19eca8af2391f172ee2 100644
--- a/components/arc/test/fake_file_system_instance.h
+++ b/components/arc/test/fake_file_system_instance.h
@@ -5,40 +5,142 @@
 #ifndef COMPONENTS_ARC_TEST_FAKE_FILE_SYSTEM_INSTANCE_H_
 #define COMPONENTS_ARC_TEST_FAKE_FILE_SYSTEM_INSTANCE_H_
 
+#include <stdint.h>
+
+#include <map>
 #include <string>
+#include <utility>
 #include <vector>
 
+#include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
+#include "base/threading/thread_checker.h"
 #include "components/arc/common/file_system.mojom.h"
 
 namespace arc {
 
-// A fake implementation which returns errors for all requests or just ignores
-// them.
+// Fake implementation to operate on documents in memory.
+//
+// ArcFileSystemOperationRunner provides two types of methods: content URL
+// based and documents provider based. According to backend type, you need
+// to setup the fake with different functions.
+//
+// Content URL based functions are:
+// - GetFileSize()
+// - OpenFileToRead()
+// Fake files for those functions can be set up by AddFile().
+//
+// Documents provider based functions are:
+// - GetDocument()
+// - GetChildDocuments()
+// Fake documents for those functions can be set up by AddDocument().
+//
+// Notes:
+// - GetChildDocuments() returns child documents in the same order as they were
+//   added with AddDocument().
+// - All member functions must be called on the same thread.
 class FakeFileSystemInstance : public mojom::FileSystemInstance {
  public:
-  FakeFileSystemInstance();
+  // Specification of a fake file available to content URL based methods.
+  struct File {
+    enum Seekable {
+      SEEKABLE,
+      NON_SEEKABLE,
+    };
 
-  // mojom::FileSystemInstance:
+    // Content URL of a file.
+    std::string url;
+
+    // The content of a file.
+    std::string content;
+
+    // Whether this file is seekable or not.
+    Seekable seekable;
+
+    File();

[hidehiko, 2017/01/27 15:50:00]

Could you get rid of map::operator[], and replace it by map::insert()?
Then, IIUC, you do not need default ctor any more.

Ditto for Document.

[Shuhei Takahashi, 2017/01/30 02:27:36]

Well, of course I know I can get rid of the default constructor, but I did not
bother to do so because implementing the default constructor is not a big deal
and having it will allow us to use this type intuitively like map::operator[].

But anyway, if you want me to do so, I can.

+    File(const std::string& url, const std::string& content, Seekable seekable);
+    File(const File& rhs);

[hidehiko, 2017/01/27 15:50:00]

IIUC, because this is not DISALLOW_COPY_AND_ASSIGN() struct, you can simply drop
declaration and definition of ctor, so that compiler will generate default
copy-ctor automatically, and this gets movable.

[Shuhei Takahashi, 2017/01/30 02:27:36]

As I wrote in earlier comment, we can't drop copy-ctor due to chromium-style
requirement.

../../components/arc/test/fake_file_system_instance.h:67:3: error:
[chromium-style] Complex class/struct needs an explicit out-of-line copy
constructor.
  struct Document {
  ^

+    ~File();
+  };
+
+  // Specification of a fake document available to documents provider based
+  // methods.
+  struct Document {
+    // Authority.
+    std::string authority;
+
+    // ID of this document.
+    std::string document_id;
+
+    // ID of the parent document. Can be nullptr string if this is a root.

[hidehiko, 2017/01/27 15:50:00]

If you use std::string, |nullptr| is out-dated comment. Could you update it?

[Shuhei Takahashi, 2017/01/30 02:27:36]

Good catch.

+    std::string parent_document_id;
+
+    // File name displayed to users.
+    std::string display_name;
+
+    // MIME type.
+    std::string mime_type;
+
+    // File size in bytes. Set to -1 if size is not available.
+    int64_t size;
+
+    // Last modified time in milliseconds from the UNIX epoch.
+    // TODO(crbug.com/672737): Use base::Time once the corresponding field
+    // in file_system.mojom stops using uint64.
+    uint64_t last_modified;
+
+    Document();
+    Document(const std::string& authority,
+             const std::string& document_id,
+             const std::string& parent_document_id,
+             const std::string& display_name,
+             const std::string& mime_type,
+             int64_t size,
+             uint64_t last_modified);
+    Document(const Document& rhs);
+    ~Document();
+  };
+
+  FakeFileSystemInstance();
   ~FakeFileSystemInstance() override;
 
+  // Adds a file accessible by content URL based methods.
+  void AddFile(const File& file);
+
+  // Adds a document accessible by document provider based methods.
+  void AddDocument(const Document& document);
+
+  // mojom::FileSystemInstance:
   void GetChildDocuments(const std::string& authority,
                          const std::string& document_id,
                          const GetChildDocumentsCallback& callback) override;
-
   void GetDocument(const std::string& authority,
                    const std::string& document_id,
                    const GetDocumentCallback& callback) override;
-
   void GetFileSize(const std::string& url,
                    const GetFileSizeCallback& callback) override;
-
   void OpenFileToRead(const std::string& url,
                       const OpenFileToReadCallback& callback) override;
-
   void RequestMediaScan(const std::vector<std::string>& paths) override;
 
  private:
+  // A pair of an authority and a document ID which identifies the location
+  // of a document in documents providers.
+  using DocumentKey = std::pair<std::string, std::string>;
+
+  base::ThreadChecker thread_checker_;
+
+  base::ScopedTempDir temp_dir_;
+
+  // Mapping from a content URL to a file.
+  std::map<std::string, File> files_;
+
+  // Mapping from a document key to a document.
+  std::map<DocumentKey, Document> documents_;
+
+  // Mapping from a document key to its child documents.
+  std::map<DocumentKey, std::vector<DocumentKey>> child_documents_;
+
   DISALLOW_COPY_AND_ASSIGN(FakeFileSystemInstance);
 };