I am writing a test method for a Visualforce extension class. One of the scenios I wantt oconfirm that a certain error message appears. The message is below. I am not sure in my System. AssertEquals parameters, what I would put? Please adivce. Thanks.

     String sMsg = 'There are not vaild Bookings. Please contact the System Admin';
           ApexPages.Message msg = new ApexPages.Message(ApexPages.Severity.INFO, sMsg);
           ApexPages.addMessage(msg);
        

i want a prev and next button on a vf page, but the next button and pre would not go to another page. It would just get the next or previous record in the list to display. any suggestions or code with a similiar functionaloilty that i could get ideas from. thank you. I am using a controller extension. for my vf page. thank you.