Problems to serialise object when using FileSystem memory

Hi,

I am writing test case that uses following strategy:

-=-=-
| memory file |
memory := FileSystem memory.
file := memory workingDirectory / 'file.fuel'.
FLSerializer serialize: {1. 2. 3} toFileNamed: file.
-=-=-

But it does not work because in StandardFileStream class>> #forceNewFileNamed: a "self fullName: fileName.” is called and it returns a string. So it tries to create the file in the default real file system; not in the memory file system. FLSerializer calls it in:

-=-=-
serialize: anObject toFileNamed: aFilename
        "Serialize the graph starting at the root object received and answers the FLSerialization object"
        StandardFileStream
                forceNewFileNamed: aFilename
                do: [ :aFileStream |
                        aFileStream binary.
                        self serialize: anObject on: aFileStream ]
-=-=-

using a stream neither work:

-=-=-
| disk file |
disk := FileSystem memory.
file := disk workingDirectory / 'file.fuel'.
file writeStreamDo: [ :aStream |
        FLSerializer serialize: {1. 2. 3} on: aStream ].
-=-=-

It produces an improper indexable object.

The only code that works is that one:
-=-=-
| file |
file := FileLocator workingDirectory / 'file.fuel'.
FLSerializer serialize: {1. 2. 3} toFileNamed: file.
-=-=-

I think that using MemoryStore is a clean way to test code that stores contents into a file.
How can I use FLSerializer and MemoryStore together?

Thanks!
Juraj