Each challenge starts with a description of the problem. We have defined a few unit tests to help you solve the logical problems, however your code will be tested against even more unit tests with presumably large numbers, strings, list if applicable. Oh and we will also test your code's performance... :)
You are not allowed to use any external dependencies. You can write as many additional unit tests as you would like. You can Google and StackOverflow as fast as you can.
Bonus challenge is worth 1 regular challenge - if you finish 5 of 6 challenges correctly in addition to bonus challenge, you can be considered a winner. ;)