I'm having trouble testing this code. It seems so simple but I can't get it to work.It keep giving me an Attempt to de-reference a null object error.

```
public CustomSetting__c instanceVariable;
public CustomSetting__c getCustomSettingInstance(){
     return instanceVariable;
}

```

EDIT: Forgot to add the test methods but here they are

```
@isTest static void test_getConfigInstance() {
    CustomSettingCtrlr myCtrlr = new CustomSettingCtrlr ();

    myCtrlr.instanceVariable.Name = 'name';
    myCtrlr.instanceVariable.booleanField= true;
    insert myCtrlr.instanceVariable;

    Test.startTest();
        myCtrlr.getConfigInstance();
    Test.stopTest();

    System.assertNotEquals(csmUtil.getConfigInstance(), null);
    System.assertEquals(myCtrlr.instanceVariable.Name, 'name');

}

```