Our existing tests run on an in memory h2 database. Which is good because it is simple to set up and the tests run fast.
We can integrate these exact same tests with MySQL and PostgreSQL (the databases that we currently support). To give a practical example of the value for this, our latest master branch of the platform fails on mysql during the setup wizard, but succeeds on postgresql. It took me a while to figure this out because our CI is green. If we had such in our pipeline, i would not have wasted that time because we would have heard CI scream on the commit that led to this. 