- New internal/fs package for testable filesystem operations - In-memory filesystem support for unit testing without disk I/O - Swappable global FS: SetFS(afero.NewMemMapFs()) - Wrapper functions: ReadFile, WriteFile, Mkdir, Walk, Glob, etc. - Testing helpers: WithMemFs(), SetupTestDir() - Comprehensive test suite demonstrating usage - Upgraded afero from v1.10.0 to v1.15.0