When you have developed a new system you want to make sure that it works properly.
One of the things that you will test is your validation rules. Lets look at an example:
Validation Rule: >=10 AND <=100
This validation rule should accept all data between (and inclusive) 10 and 100
You would test this rule by entering some extreme data - right on the edges or near to the edges of the validation rule.
Extreme data in this case could be 10, 11, 99, 100
If the system is working properly then it should accept the extreme data.
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Extreme Data