I have a very simple hotel management simple on the console and i am required to do its BlackBox testing. but I am clueless here. What can I test in a simple app like this??
Black box testing simply means you only care about the inputs and outputs of your program and you could care less about the inner workings.
First, determine all of the input and output variables. Then, try your program with all variations of inputs (this usually isn't possible, so test a lot of inputs) and verify that you get the correct output.