Hi,
I am facing an issue for writing a test class for a invocable method which is getting called by Process Builder.
Actual class--
public class vOppDuplicate {
//public virtual class BaseException extends Exception {}
//public class OtherException extends BaseException {}
@InvocableMethod (label='Records for duplicate' description='Duplicate Check')
public static void updateOppDup(List<Id> OpportunityIds) {
try{
        List<Opportunity> oppList = [SELECT Opp_Acc_Concatenate__c,Opportunity_Unique_Name__c FROM Opportunity WHERE Id in :OpportunityIds];
        for(Opportunity opp: oppList)
         {
           opp.Opportunity_Unique_Name__c = opp.Opp_Acc_Concatenate__c;               
         } 
          update oppList;
        //return oppList;
    }
    catch(DMLException e)
    {
        //throw new OtherException('Duplicate value is present');
        throw new DMLException('Duplicate value with same opportunity and account name already present.'+'<br/>');
        //System.debug('The following exception has occurred: ' + e.getMessage());
        //if(e.getMessage().contains('Update failed')){
        //e.setMessage('Duplicate value is already present.');
        //ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.Error, e.getMessage()));
    //}

    }
    }
}

Test Class---
@isTest
private class vOppDuplicateTest {
@isTest static void testdup() {
    Account acc = new Account(name='TestClient');
    insert acc;
    Opportunity oppList = new Opportunity(Opportunity_Unique_Name__c= 'DupAccOppTest', Name = 'OppDup',AccountId=acc.Id);
    insert oppList;
    //oppList = [SELECT Id from Opportunity where Id = : oppList.Id];
    vOppDuplicate oppdup = new vOppDuplicate();
    //oppdup.updateOppDup();
}
}

How do i call the method and pass the value ?

Thanks