Download the zip file which comes with the problem; it should be available on the IOI website and in many judges as well (oj.uz has it on the right side when you open the problem). The zip file will contain a compile script, along with templates and a grader which will allow you to test the problem on your own inputs. The grader details are usually given in the problem statement itself.

You can also download all data (graders, solutions, testcases, etc.) for all problems for a specific year from the IOI website. If you want to test your solution locally completely (as in get the verdict), just write a script to run your program through the grader based on all the testcases given.