Challenge 2

- [Instructor] Now before we go on,…I want to just mention…that in this instance, we've used an unchecked exception,…this number format exception.…We might discover later that there is a requirement…to make this a checked exception.…If that turns out to be the case,…we will need to change this.…But unless we know that that is the requirement,…what we have is fine.…And I'm pointing this out…because I think this is quite a good example…of the kind of thing that happens…in test-driven development.…

We don't really know all the business requirements…in detail.…We're building with what we do know.…But if we discover later…that a checked exception is required,…we can change this…and we can use the test that we've built…to check that nothing else is impacted by this change.…Now at this stage, you could if you wanted,…create more tests to check 11-digit numbers,…or eight-digit numbers,…but I think that is a waste of time.…We know that our number format exception is going…to be flown if the length of the string is not 10 digits…