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.â 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