public void ファイル長_SetLength()
        {
            var path = @"z:\temp\aaa.txt";
            var text = "aaa";
            var encoding = Encoding.GetEncoding("shift-jis");

            var file = new FileEmu();
            file.AddFile(path, text, encoding);
            Assert.AreEqual(3, file.GetLength(path));

            file.SetLength(path, 10);
            Assert.AreEqual(10, file.GetLength(path));
        }