public async Task UpgradeInstance()
{
FilePath filePath = "test.txt";
var file = new FileModel();
file.CreateNew();
await file.SetContent(TestHelper.ToStream("Foo"));
await file.LinkToFile(filePath);
await registry.ShareModel(file);
var textFile = await registry.GetSharedModel <TextFileModel> (filePath);
Assert.IsFalse(textFile.IsLoaded);
await textFile.Load();
Assert.AreEqual("Foo", textFile.GetText());
var textBufferFile = await registry.GetSharedModel <TextBufferFileModel> (filePath);
Assert.IsFalse(textBufferFile.IsLoaded);
await textBufferFile.Load();
Assert.AreEqual("Foo", textBufferFile.GetText());
}