How to setup cobra and viper for test configurations in golang

We have a binary we are starting which has several subcommands, all set up with cobra. And we want to use viper for configuration. So the initialization of this is setup according to the docs:

func init() {
    cobra.OnInitialize(initConfig)    

    RootCmd.PersistentFlags().StringVarP(&loglevel, "loglevel", "l", "info", "Default log level")
    //other persistent flags    
    viper.BindPFlags(RootCmd.PersistentFlags())

    log.CreateLogger(loglevel)

    //add all other subcommands
    RootCmd.AddCommand(...)
}

My issue is with initConfig:

func initConfig() {
    if cfgFile != "" {
        // Use config file from the flag.
        viper.SetConfigFile(cfgFile)
    } else {
        // Find home directory.
        home, err := homedir.Dir()
        if err != nil {
            handleError(err)
            os.Exit(1)
        }
        confDir = filepath.Join(home, DefaultConfigDir)
        viper.Set("configDir", configDir)

        viper.SetConfigName("config")
        viper.SetConfigType("json")
        viper.AddConfigPath(configDir)
        viper.AddConfigPath(".")

        cfgFile = filepath.Join(configDir, "config.json")
    }

    viper.AutomaticEnv()

    if err := viper.ReadInConfig(); err != nil {
        if _, ok := err.(viper.ConfigFileNotFoundError); ok {
            // Config file not found; ignore error if desired               l
            err := os.Mkdir(cfgDir, os.ModePerm)
            if err != nil {
                handleError(err)
            }
            err = viper.WriteConfigAs(cfgFile)
            if err != nil {
                handleError(err)
            }
        } else {
            handleError(err)
            os.Exit(1)
        }
    }
}

This runs inside init, and this is in my subcommands package - so my subcommands tests will run this init as well.

Trouble is it looks for the home folder, and of course may mess with existing configs. In other words, I don't want this for testing, I want a clean testing directory.

How can I achieve this? As it has to run inside init because of the flags and the early initialization of configs, I have not been able to figure out an alternative.