popen_spec: add tests for `safe_popen_read` and `safe_popen_write`
popen_spec: add tests for `safe_popen_read` and `safe_popen_write`

JCount/brew,vitorgalvao/brew,EricFromCanada/brew,MikeMcQuaid/brew,JCount/brew,vitorgalvao/brew,vitorgalvao/brew,vitorgalvao/brew,MikeMcQuaid/brew,claui/brew,nandub/brew,nandub/brew,claui/brew,nandub/brew,Homebrew/brew,sjackman/homebrew,sjackman/homebrew,Homebrew/brew,Homebrew/brew,EricFromCanada/brew,claui/brew,sjackman/homebrew,JCount/brew,claui/brew,MikeMcQuaid/brew,EricFromCanada/brew,MikeMcQuaid/brew,nandub/brew,JCount/brew,EricFromCanada/brew,Homebrew/brew,sjackman/homebrew