how to be sure the test runs only against data from fixtures

AbstractIntegrationSpec.groovy

abstract class AbstractIntegrationSpec extends IntegrationSpec {

    @Shared
    def fixtureLoader, fixtures, initCatalogueService, sessionFactory

    def loadFixtures(){
        String scriptLocation = "${System.getProperty('java.io.tmpdir')}mc/testdata.sql"

        def sql = new Sql(sessionFactory.currentSession.connection())

        if (new File(scriptLocation).exists()) {
            long start = System.currentTimeMillis()
            sql.execute("RUNSCRIPT FROM ${scriptLocation}")
            sessionFactory.currentSession.clear()
            println "database restored from in ${scriptLocation} ${System.currentTimeMillis() - start} ms"
            return
        }

        long start = System.currentTimeMillis()
        String clearScriptLocation = "${System.getProperty('java.io.tmpdir')}mc/drop.sql"
        sql.execute("SCRIPT NODATA DROP TO ${clearScriptLocation}")
        println "Clear script created in $clearScriptLocation"
        sql.execute("RUNSCRIPT FROM ${clearScriptLocation}")
        println "Database cleared from $clearScriptLocation"

        initCatalogueService.initDefaultRelationshipTypes()
        println "loading fixtures"
        fixtures = fixtureLoader.load("assets/*", "batches/*", "dataTypes/*", "enumeratedTypes/*", "measurementUnits/*", "models/*", "relationshipTypes/*", "classifications/*").load("actions/*", "valueDomains/*", "users/*").load("dataElements/*").load("extensions/*", "mappings/*").load("csvTransformations/*")
        sessionFactory.currentSession.flush()

        sql.execute("SCRIPT DROP TO ${scriptLocation}")
        println "Data script created in $scriptLocation"
        println "database created in ${System.currentTimeMillis() - start} ms"
    }

}