How to mock/abstract filesystem in go?

Question

I would like to be able to log every write/read that my go app issues to the underlying OS, and also (if it's possible) completely replace FS with one that resides only in memory.

Is it possible? How? Maybe there is a ready-to-Go solution?

Answer 1

This is straight from Andrew Gerrand's 10 things you (probably) don't know about Go:

var fs fileSystem = osFS{}  type fileSystem interface {     Open(name string) (file, error)     Stat(name string) (os.FileInfo, error) }  type file interface {     io.Closer     io.Reader     io.ReaderAt     io.Seeker     Stat() (os.FileInfo, error) }  // osFS implements fileSystem using the local disk. type osFS struct{}  func (osFS) Open(name string) (file, error)        { return os.Open(name) } func (osFS) Stat(name string) (os.FileInfo, error) { return os.Stat(name) } 

For this to work, you will need to write your code to take a fileSystem argument (maybe embed it in some other type, or let nil denote the default filesystem).