Golang afero

Afero defines and implements an interface to access the filesystem.
You can then pass in an abstraction of real os calls, or a stub stub interface you can make assertions against.

Documentation

api docs	https://pkg.go.dev/github.com/spf13/afero
github	https://github.com/spf13/afero

Usage

Basics

import "github.com/spf13/afero"

appfs := afero.NewOsFs()     // real 'os' calls
appfs := afero.NewMemMapFs() // memory backed fake filesystem
// there are several additional options, like sftp, CopyOnWriteFs, ...

// creates on disk, or in memory (depending on appfs val)
appfs.Create("/var/tmp/foo.txt")

// utils exposed in different imports
import "afero/ioutil"
ioutil.ReadFile(appfs, "/var/tmp/foo.txt")

There are no assertions, when testing use the API to check the presence/contents of the file.
There are however some additional utils that are helpful, both in testing and production code (ex. appfs.DirExists()).