It turns out that we don't have to specify the AutoMigration classes anymore in the runMigrationsAndValidate method. It is applied automatically to the database just like it is done in the real application database.

@get:Rule
    val helper: MigrationTestHelper = MigrationTestHelper(
        InstrumentationRegistry.getInstrumentation(),
        Database::class.java,
    )

...

@Test
fun testAutoMigration() {
db = helper.runMigrationsAndValidate(TEST_DB, 2, true)
// verify
}