How to test the number of database calls in Rails

Using database: How to test the number of database calls in Rails on newest questions tagged database – Stack Overflow

I am creating a REST API in rails. I’m using RSpec. I’d like to minimize the number of database calls, so I would like to add an automatic test that verifies the number of database calls being executed as part of a certain action.
Is there a simple way to add that to my test?
What I’m looking for is some way to monitor/record the calls that are being made to the database as a result of a single API call.
If this can’t be done with RSpec but can be done with some other testing tool, that’s also great.

source: http://stackoverflow.com/questions/11222942/how-to-test-the-number-of-database-calls-in-rails
Using database: using-database