@isTest

public class BatchSkillExcalationUpdaterTest {
    static testMethod void ValidateUpdates() {

        ...
        EscalationSkillUpdater SkillBatch = new EscalationSkillUpdater();
        system.debug(logginglevel.FINEST, 'BATCHING...');
        Database.executeBatch(SkillBatch);
        system.debug(logginglevel.FINEST, 'FINISHED BATCHING.');
        ...
    }
}

global class EscalationSkillUpdater implements Database.Batchable <sObject> {
    global Database.QueryLocator start (Database.BatchableContext BC) {
        ...
        return Database.getQueryLocator(query);
    }

    global void execute (Database.BatchableContext BC, list<SkillEscalationChangeRecord__c> Data) {
        ...
        System.debug(logginglevel.FINEST, 'FLAG');
        update Data;
    }

    global void finish (Database.BatchableContext BC) {}
}