private static async ValueTask <ISingletonFileSystem> TestFileSystem()
    {
        var fileSystem = new MemoryFileSystem(new NullFileEventService());
        var root       = await fileSystem.CreateFileHandle(Url.Parse("file://test/"));

        var foo = await fileSystem.CreateDirectory(root, "foo");

        var bar = await fileSystem.CreateDirectory(foo, "bar");

        var dir = await fileSystem.CreateDirectory(bar, "dir");

        await fileSystem.CreateFile(bar, "a", Convert.FromHexString("010203"));

        await fileSystem.CreateFile(bar, "b", Convert.FromHexString("010203"));

        await fileSystem.CreateFile(bar, "c", Convert.FromHexString("010203"));

        await fileSystem.CreateFile(dir, "a", Convert.FromHexString("010203"));

        await fileSystem.CreateFile(dir, "b", Convert.FromHexString("010203"));

        return(fileSystem);
    }