Automatically checks if your code passes the given sample cases or not on Codeforces.You no longer have to manually run your code, type in the sample inputs and see if your output matches the sample outputs or not. This extension will do it for you!
It'll save you a lot of time and effort especially during a contest so that you can focus more on the contest itself and less on testing your code against the sample cases before submitting it.
It's also very helpful when problems have multiple sample cases and/or lengthy inputs and outputs.
Reviews of Codeforces Sample Case Tester extension