Dear Gurus,

This is about a Apex DML exception which is troubling

23:43:49:014 EXCEPTION_THROWN [49]|System.DmlException: Insert failed. First exception on row 0; first error: REQUIRED_FIELD_MISSING, Required fields are missing: [Level 1, Case]: [Level 1, Case]

Here is apex code-->

public class PickListHandler {
    @AuraEnabled
    public static List<String> getLevel1(){
    List<String> tempLst1 = new List<String>();
        for(AggregateResult  ar : [select Level_1__c,COUNT(id) from Case_Type_Data__c  group by Level_1__c])
    {
        tempLst1.add(''+ar.get('Level_1__c'));
    }

    return tempLst1;
      
      
    } 
    
    @AuraEnabled
    public static List<String> getLevel2(string strName){
    List<String> tempLst2 = new List<String>();
       for(AggregateResult  ar : [select Level_2__c,COUNT(id) from Case_Type_Data__c where Level_1__c=:strName  group by Level_2__c])
    {
       tempLst2.add(''+ar.get('Level_2__c'));
    }

    return tempLst2;
      
    } 
    
    @AuraEnabled
    public static List<String> getLevel3(string strName1,string strName2){
     List<String> tempLst3 = new List<String>();
      for(AggregateResult  ar : [select Level_3__c,COUNT(id) from Case_Type_Data__c  where Level_1__c=:strName1 and Level_2__c=:strName2 group by Level_3__c])
    {
       tempLst3.add(''+ar.get('Level_3__c'));
    }

    return tempLst3;
      
      
    } 
         
     @AuraEnabled
     public  static String  savecasetype(string level1,string level2,string level3,string caseid){
     string strMsg='successfull';
          try{
     ERT_Case_Type__c obj=new ERT_Case_Type__c();
     Obj.Case__c =caseid;
     Obj.Level_1__c=level1;
     Obj.Level_2__c=level2;
     Obj.Level_3__c=level3;
     Insert obj;
     Return 'Successfully Inserted Levels';
     }
     
    catch(Exception ex){
            strMsg='error';
        }
     return strMsg;  
}
    
     
    
    

}

Hereis working Test class for above apex-->

@isTest
public class testGetAllLevels { 

static testMethod void testGetLevel1()
{
    Case_Type_Data__c obj = new Case_Type_Data__c();
    obj.Level_1__c = 'Test Level 1';
    insert obj;
    List<String> s = PickListHandler.getLevel1();

}
    
static testMethod void testGetLevel2()
{
    Case_Type_Data__c obj = new Case_Type_Data__c();
    obj.Level_1__c = 'Test Level 1';
    insert obj;
    List<String> s = PickListHandler.getLevel2('Test Level 1');

}
    
static testMethod void testGetLevel3()
{
    Case_Type_Data__c obj = new Case_Type_Data__c();
    obj.Level_1__c = 'Test Level 1';
    obj.Level_2__c = 'Test Level 2';
    obj.Level_3__c = 'Test Level 3';
    insert obj;
    List<String> s = PickListHandler.getLevel3('Test Level 1','Test Level 2');

}
    
    
static testMethod void testsaveCaseType(){
        // Create the Case Record.
        Case cas = new Case(Status ='New', Priority = 'Medium', Origin = 'Email'); 
        insert cas;
       
        ERT_Case_Type__c obj=new ERT_Case_Type__c();
        string one='one';
        string two='two';
        string three='three';
        test.startTest();
        String testing=PickListHandler.savecasetype(one,two,three,cas.id);
        test.stopTest();
    }
    

    
 
    
}

Here is lightning component JS -->

({
    doInit : function(component, event, helper) {
        var action = component.get("c.getLevel1");
        action.setCallback(this, function(e) {
            if(e.getState()=='SUCCESS'){
                var result=e.getReturnValue();
                component.set("v.lstLevel1",result);
            }
        });
        $A.enqueueAction(action);
    },    
    getLvl1:function(component, event, helper){
       
        var picklist=component.find('ddLevel1');
        var picklistvalue=picklist.get('v.value');
        var action = component.get("c.getLevel2");
        //alert('called'+picklistvalue);
        action.setParams({  'strName' : picklistvalue  });//
        action.setCallback(this, function(e) {
            if(e.getState()=='SUCCESS'){
                var result=e.getReturnValue();
                component.set("v.lstLevel2",result);
            }
        });
        $A.enqueueAction(action);
        //  alert(picklistvalue);
    },
    getSelectedValue:function(component, event, helper){
        var picklist=component.find('ddLevel1');
        var picklistvalue=picklist.get('v.value');
        var picklistdep=component.find('ddLevel2');
        var picklistvaluedep2=picklistdep.get('v.value');
        var action = component.get("c.getLevel3");
       // alert(picklistvaluedep2+' called'+picklistvalue);
        action.setParams({  'strName1' : picklistvalue,
                         'strName2' : picklistvaluedep2});//
        action.setCallback(this, function(e) {
            if(e.getState()=='SUCCESS'){
                var result=e.getReturnValue();
                component.set("v.lstL3",result);
            }
        });
        $A.enqueueAction(action);
       // alert(picklistvalue+'  '+picklistvaluedep);
    },
    onConfirm:function(component, event, helper){
        var picklist=component.find('ddLevel1');
        var picklistvalue=picklist.get('v.value');
        var picklistdep=component.find('ddLevel2');
        var picklistvaluedep2=picklistdep.get('v.value');
       
        var picklistdep3=component.find('ddLevel3');
        var picklistvaluedep3=picklistdep3.get('v.value');
        var action = component.get("c.savecasetype");
        
        action.setParams({  'strName1' : picklistvalue,
                          'strName2' : picklistvaluedep2,
                          'strName3' : picklistvaluedep3,
                          'id' : component.get("v.recordId")});//
                          
        
        var toastEvent = $A.get("e.force:showToast");
       //alert('abcd');
        action.setCallback(this, function(e) {
            if(e.getState()=='SUCCESS'){
                var result=e.getReturnValue();
                // alert(result);
                if(result==='successfull'){
                    toastEvent.setParams({
                        "title": "Success!",
                        "message": "The record has been inserted  successfully."
                    });
                    toastEvent.fire();
                }else{
                    toastEvent.setParams({
                        "title": "Error",
                        "message": "The record has not been inserted  successfully."
                    });
                    toastEvent.fire();
                }
            }
        });
        $A.enqueueAction(action);
       
    }
})

Here is Apex handler -->

<aura:component controller="PickListHandler" implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes,force:lightningQuickAction" access="global" >
    <!-- Actions-->
    <aura:handler name="init" value="{!this}" action="{!c.doInit}" />
    <!-- variable-->
    <aura:attribute name="lstLevel1" type="String[]" />
     <aura:attribute name="lstLevel2" type="String[]" />
      <aura:attribute name="lstL3" type="String[]" />
    <span> Level 1</span>
    <ui:inputSelect aura:id="ddLevel1" change="{!c.getLvl1}">
        <ui:inputSelectOption label="-Select-" value="true"/>        
        <aura:iteration items="{!v.lstLevel1}" var="value">          
            <ui:inputSelectOption label="{!value}" text="{!value}" />
        </aura:iteration>
    </ui:inputSelect>
    <span>Level 2</span>
    <ui:inputSelect aura:id="ddLevel2" change="{!c.getSelectedValue}">
        <ui:inputSelectOption label="-Select-" value="true"/>        
        <aura:iteration items="{!v.lstLevel2}" var="value">          
            <ui:inputSelectOption label="{!value}" text="{!value}" />
        </aura:iteration>
    </ui:inputSelect>
     <span>Level 3</span>
    <ui:inputSelect aura:id="ddLevel3" >
        <ui:inputSelectOption label="-Select-" value="true"/>        
        <aura:iteration items="{!v.lstL3}" var="value">          
            <ui:inputSelectOption label="{!value}" text="{!value}" />
        </aura:iteration>
    </ui:inputSelect>
    <lightning:button variant="brand" label="Save" onclick="{!c.onConfirm}" />
</aura:component>

Now when i run test class basically create a case and pass the id to apex class,i see no issues but issue comes only when i click 'Save',i see ""The record has not been inserted successfully."" On checking Logs i found DML exception as below

23:43:49:014 EXCEPTION_THROWN [49]|System.DmlException: Insert failed. First exception on row 0; first error: REQUIRED_FIELD_MISSING, Required fields are missing: [Level 1, Case]: [Level 1, Case]

Please note in this scenarion Each case can have multiple ERT_Case_Type__c and each ERT_Case_Type__c can have multiple Case_Type_Data__c

Please help in finding  resolution.

Thanks in Advance
Carolyn