Test Writing: String Rotate Right

Created By: Geoffrey Challen

/ Version: 2020.9.1

This problem combines Strings, functions, and arrays. Super fun!

Write a function called rotateRight that takes a nullable String as its first argument and a non-negative Int as its second argument and rotates the String by the given number of characters. Here's what we mean by rotate:

• CS125 rotated right by 1 becomes 5CS12
• CS125 rotated right by 2 becomes 25CS1
• CS125 rotated right by 3 becomes 125CS
• CS125 rotated right by 4 becomes S125C
• CS125 rotated right by 5 becomes CS125
• CS125 rotated right by 8 becomes 125CS

And so on. Notice how characters rotated off the right end of the String wrap around to the left.

This problem is tricky! Here are a few hints:

1. You will want to use the remainder operator to perform modular arithmetic.
2. You will probably want to convert the String to an array of characters before you begin.
3. You can convert an array of characters characters back into a String like this: String(characters).
4. You can also solve this problem quite elegantly using substring.

If the passed String argument is null, you should return null. Good luck and have fun!

Test Design Challenge

You're challenge is to write tests for this problem described above.

• Provide a method named test that accepts no arguments and does not return a value.
• If the implementation of the class described above is incorrect, your test method should throw an exception.
• If it is correct, do not throw an exception.
• You may want to use Kotlin's assert or check methods