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..75fce058ef9030db1b9dde3ace66c347a9c0cd94 100644
--- a/components/arc/test/fake_file_system_instance.h
+++ b/components/arc/test/fake_file_system_instance.h
@@ -5,40 +5,140 @@
 #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 class Seekable {
+      YES,

[hashimoto, 2017/01/30 03:29:10]

How about swapping the order (i.e. NO, YES) to make NO equal to 0?
It should result in less confusing code.

+      NO,
+    };
 
-  // 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(const std::string& url, const std::string& content, Seekable seekable);
+    File(const File& rhs);

[hashimoto, 2017/01/30 03:29:10]

"rhs" doesn't make sense in a ctor.

[Shuhei Takahashi, 2017/01/30 03:39:16]

Pro tip: Just "does not make sense" in review comments does not make sense.
Please suggest an alternative.

[hidehiko, 2017/01/30 05:21:57]

FYI:
I'm fine with either "rhs" or "that" as it is already used in Chromium.
According to git grep, "other" looks more popular in Chromium? Or, another
pattern is repeating the class name (e.g. File(const File& file), Document(const
Document& document)).

cf) "git grep -e ' \([a-zA-Z0-9]\+)(const \1&'"

+    ~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 empty if this is a root.
+    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(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);
 };