What is the best approach to testing rules in the database?

What is the best approach to testing rules in the database? We have a system which returns the value based on the created rule.

ex. Ruel 1: Client A family size is less than 2 and income is less than < 2000 $ per annum then help him by 500 $. Rule 2: Client B family size is less than 3 and income is less than < 4000 $ per annum and he does not use electricity for heating purpose then help him by 500 $.

like that, there are 5000 rules, and the set of rules also different for the different agency.

I need to check all rules positive/negative scenario for all clients.

What should be the best approach to test it?