You can debug your program by printing debug statements to Standard Output (STDOUT). The debug output appears in the Your Output section for the questions that require you to write the full program. In such cases, remove all your debug statements before submitting your solution because the entire output is matched with the expected output.
For questions that expect you to complete a function, all your print statements are captured separately in the Debug Output section. These print statements are ignored when your output is compared with the expected output. You must ensure that you return the expected output.
Some problems also allow you to give you an option to 'Test against custom input': you can use this option to specify your own Standard input (STDIN) values to run your test against. When you select this checkbox, no other test cases are executed.