How to write unittest for database classes?

Assuming that you have different method that takes care of creating connection to DB, you need to create an object of type Customer in your test class and need to have the properties name, firstname, address on that object.

There are different ways to verfiy record was inserted into table.

For example, either you can rely on count or you can pull the inserted object and then compare those two .

First make a method call that returns number of records in the table.

Once you do that make a call to insertCustomer method.

For assertion, try calling the first method again to check records in the same table. If this count is one more than previous one, it is good, else it failed.