You are right that the SpringLiquibase setup should do the database update automatically, but it will only do it when the spring framework is started.
My guess is that your normal application startup fires Liquibase through Spring but the test framework does not. Perhaps they had not noticed it because they would tend to make the database change in the liquibase changelog files, then start the normal application for initial testing (which updated the database) then build and run the tests. Now that you are running the tests first, the database is not yet there.
Are you able to tell if your tests are trying to start Spring?
Even in cases where an application is using SpringLiquibase, I usually recommend configuring your project to allow manual updates using liquibase-maven-plugin, ant plugin, or command line because it tends to make a more efficient process. With that setup, you can add changesets and then run liquibase update without going through an entire application startup or even running your tests. You could set it to automatically run on test execution, but the update process is usually infrequent enough that it is better to avoid the liquibase update overhead on every test execution. It is still very helpful to include in your application's spring setup so that in QA and production you don't have to remember to manually update the database, it is just automatically kept up to date.