@isTest
private class testBeforeInsertUpdateOnUser {

    static testMethod void myUnitTest() {
        User targetUser = [SELECT Id, LastName, FirstName, Alias, Alias__c FROM User WHERE Id = :userInfo.getUserId()];
        targetUser.LastName = 'last';
        targetUser.FirstName = 'First';
        update targetUser;
        User targetUser02 = [SELECT Id, LastName, FirstName, Alias, Alias__c FROM User WHERE Id = :userInfo.getUserId()];
        System.assertEquals( 'lastFirst', targetUser02.Alias__c, '001');
    }
}