I am trying to run a test but I keep getting the same error that the Address field is empty or missing. When I add a !Test,isRunning I get the following error msg. But the actual class works beautifully in dev. I am trying to get my test coverage up and apply the proper unit test. The actual class is below.

This is the test class

Error message:

 You cannot call addFields when the data is being passed into the controller by the caller.

OR:

13:33:29:311 FATAL_ERROR System.EmailException: SendEmail failed. First exception on row 0; first error: REQUIRED_FIELD_MISSING, Missing target address (target, to, cc, bcc): []

when I add the following code
 

if(!Test.isRunningTest()){
             sc.addFields(new List<String>{'CaseAssignedOwner__c'});
        }

@isTest
public class testCaseForm1747SendMail {
    static testMethod void testSend(){
       
        Case testCase = new Case();
        testCase.Subject = 'unittest';
        testCase.Description = 'unit test description';
        testCase.CaseAssignedOwner__c = 'klanguedoc@jdi.jubl.com';
        testCase.Case_Category__c = 'Product Enquiry';
        insert testCase;
            
        ApexPages.StandardController sc = new ApexPages.StandardController(testCase);
        // test constructor;
        // testCaseForm1747SendMail

        
       
    
        CaseForm1747SendMail Send1747 = new CaseForm1747SendMail(sc);
        sc.addFields(new List<String>{'CaseAssignedOwner__c'});
       
        send1747.send();
        
        
    }
}

Actual class : works fine
 

public class CaseForm1747SendMail {
    private final Case c;
    public CaseForm1747SendMail(ApexPages.StandardController stdCrlr){
   		if (!Test.isRunningTest()) { 
            stdCrlr.addFields(new List<String>{'CaseAssignedOwner__c'});

        }           
        this.c = (Case)stdCrlr.getRecord();
       
        
    }
    public Case getCase(){
        return c;
    }
   
     public PageReference send() {
        // Define the email
        Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage(); 

        // Reference the attachment page and pass in the case ID
        PageReference pdf =  Page.SendQA1747asPDF;
        pdf.getParameters().put('id',(String)c.id); 
        pdf.setRedirect(true);

        // Take the PDF content
        //Blob b = pdf.getContent();
         Blob b = Test.isRunningTest() ? Blob.valueOf('UNIT.TEST') : pdf.getContent();

        // Create the email attachment
        Messaging.EmailFileAttachment efa = new Messaging.EmailFileAttachment();
        efa.setFileName(c.CaseNumber + '.pdf');
        efa.setBody(b);
        String[] toAddresses = new List<String>();
        Case_Owner__c[] assignedOwner = new List<Case_Owner__c>();

		System.debug(c.CaseAssignedOwner__c);
       assignedOwner =  [select  MemberEmail__c from Case_Owner__c where Queues__c = : c.CaseAssignedOwner__c ];
         for(Case_Owner__c em : assignedOwner){
            toAddresses.add(String.valueOf(em.MemberEmail__c));
         }
       System.debug(toAddresses);
       
        email.setSubject( c.Subject );
             
        email.setToAddresses( toAddresses );
        email.setPlainTextBody( c.Description );

        email.setFileAttachments(new Messaging.EmailFileAttachment[] {efa});

        // Sends the email
        Messaging.SendEmailResult [] r = 
            Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email});   
        
        PageReference casePage = new ApexPages.StandardController(c).view();
        casePage.setRedirect(true);
        
        List<Task> tasks = new List<Task>();
        tasks.add(new Task(
    ActivityDate = Date.today(),
    Subject='Envoyé formulaire 1747 pour le Case ' + c.CaseNumber,
    WhatId = c.Id,
    OwnerId = UserInfo.getUserId(),
    Status='Complété - Completed'));

insert tasks;
        return null;
    }
    
}