Including a real DB in continuous integration is a must for any development IMO. (And these days usually very easy to throw up a database using Docker -- each of our full CI runs runs in 2 minutes and does hundreds of "create database" calls and populate real SQL databases from scratch..)

For instance:

1) You want to implement idempotency in your backend by using uniqueness constraints in your DB 2) That's important to test 3) That's not really tested unless you include a real DB

After including a real DB in our CI setup I will never move back.