This approach tests all possible combinations of end-user actions. Black box testing assumes no knowledge of code and is intended to simulate the end-user experience. You can use sample applications to integrate and test the application block for black box testing. You can begin planning for black box testing immediately after the requirements and the functional specifications are available.
for a black box test you give it and input and compare it with the expected output e.g. when you make a user forum it should come out with and output of user created successfully.