Unit testing in rails using factory_girl

I am trying to unit test a method inside a model as shown below in rails. The whole aim is to do a database independent testing here and so thinking of using Factory girl.

For eg.,

Class A < ActiveRecord::Base 
       def method_A(param1,param2) do
         /*do a select query on a table with param1 and param2*/
       end

end

How to go about testing the method here with arguments here. Any help would be appreciated.