This issue can be tested in webapp, Android or iOS. It doesn't require to be tested on each platform. Open a forum with an user that is not a part of the required group membership you should be able to see the warning: "Adding discussions to this forum requires group membership."  Open a forum with an user without permission to add a discussion. You should be able to see the warning: "You do not have permission to add a new discussion topic for all participants." Open a forum of type "Each person posts one discussion". The following message should be displayed: "This forum allows each person to start one discussion topic." Open a forum of type "Post threshold for blocking". You should be able to see the message: "This forum has a limit to the number of forum postings you can make in a given time period [...] "