How can I unsubscribe a NLog target

I don't know why RemoveTarget doesn't work. But if you remove the target from each rule the test passes:

Because of = () =>
{
    foreach (var rule in config.LoggingRules)
    {
        rule.Targets.Remove(target);
    }        
    Logger.Info("Test");
};

And if you remove the LoggingRule instead of the target it also works:

public class when_stopping_to_listen
{
    //...
    static LoggingRule rule;

    Establish context = () =>
    {
        //...
        rule = new LoggingRule("*", LogLevel.Trace, target);
        config.LoggingRules.Add(rule);    
        LogManager.Configuration = config;
    };

    Because of = () =>
    {
        var config = LogManager.Configuration;
        config.LoggingRules.Remove(rule);
        LogManager.Configuration = config;
        Logger.Info("Test");
    };      

    //...
}

NLog ver. 4.5 fixes LoggingConfiguration.RemoveTarget so it removes target from all registered LoggingRules.

See also: https://github.com/NLog/NLog/pull/2549