The rules are as follows:
- If the phone number is less than 10 digits assume that it is bad number
- If the phone number is 10 digits assume that it is good
- If the phone number is 11 digits and the first number is 1, trim the 1 and use the last 10 digits
- If the phone number is 11 digits and the first number is not 1, then it is a bad number
- If the phone number is more than 11 digits assume that it is a bad number
We've provided tests, now make them pass.
Hint: Only make one test pass at a time. Disable the others, then flip each on in turn after you get the current failing one to pass.