[SalesForce] Visualforce Controller Extension Test – Error: Invalid Type

I have created a fairly basic VF page and controller extension class as follows. I am trying to write a test class so that this can be deployed, but keep getting an "invalid type" error in the test class.

I have spent hours trying to figure out why. Any help would be appreciated.

Thanks,

Visualforce Page

<apex:page standardController="vlocity_cmt__Element__c" recordSetVar="Element" sidebar="false" extensions="ElementSort" >

<apex:includeScript value="{!$Resource.UtilJS}" />
<apex:form >
<apex:pageBlock >
    <apex:pageMessages />
    <apex:pageBlock >
        Note: All modifications made on the page will be lost if Return button is clicked without clicking the Save button first. 
    </apex:pageBlock>
    <apex:pageBlockButtons >
        <apex:commandButton value="Save" action="{!save}"/>
        <apex:commandButton value="Return" action="{!cancel}"/>
    </apex:pageBlockButtons>
    <apex:pageBlockTable value="{!Element}" var="a" id="table">
        <apex:column headerValue="Name">
            <apex:inputField value="{!a.name}"/>
        </apex:column>
        <apex:column headerValue="Type">
            <apex:inputField value="{!a.vlocity_cmt__Type__c}"/>
        </apex:column>
        <apex:column headerValue="Order">
            <apex:inputField value="{!a.vlocity_cmt__Order__c}"/>
        </apex:column>
        <apex:column headerValue="Parent Element">
            <apex:inputField value="{!a.vlocity_cmt__ParentElementId__c}"/>
        </apex:column>
    </apex:pageBlockTable>
</apex:pageBlock>
</apex:form>
</apex:page>

Class

public class ElementSort
 {
  public list<vlocity_cmt__Element__c> elementList{get;set;}
  public ApexPages.StandardSetController standardController;
  private Set<Id> elementIds = new Set<Id>();

  public ElementSort(ApexPages.StandardSetController standardController){
      this.standardController = standardController;
      elementList = new List<vlocity_cmt__Element__c>();
      for (vlocity_cmt__Element__c elm : (List<vlocity_cmt__Element__c>)standardController.getSelected()){ 
          elementIds.add(elm.Id);
      }
    elementList = [SELECT Name,vlocity_cmt__Type__c,vlocity_cmt__Order__c,vlocity_cmt__ParentElementId__c FROM vlocity_cmt__Element__c WHERE ID IN: elementIds ORDER BY vlocity_cmt__Order__c ];
    }
}  

Test

@isTest
public class testElementMassEdit{

public static testMethod void testElementMassEdit(){

    PageReference pageRef = Page.MassEditElement;
    Test.setCurrentPage(pageRef);

    vlocity_cmt__OmniScript__c objVOS = new vlocity_cmt__OmniScript__c();

    objVOS.Name = 'Test';
    insert objVOS;

    vlocity_cmt__Element__c objElement = new vlocity_cmt__Element__c();

    objElement.vlocity_cmt__OmniScriptId__c = objVOS.Id;
    objElement.Name = 'Test Element';
    objElement.vlocity_cmt__Type__c = 'Step';
    objElement.vlocity_cmt__Order__c = 1;

    insert objElement; 

    ApexPages.StandardController theElements = new ApexPages.StandardController(objElement);

    //* Getting "Error: Compile Error: Invalid type: myExtension here:
    myExtension ext = new myExtension(theElements);


    }
}