I want to begin by saying I am very new to salesforce and deploying code on salesforce, so this question might be very rudimentary at its core. That being said, I need assistance creating a test class for some code I have developed. This code reachs out to an external server to pull a JSON file that contains some user prefrences I want to import into salesforce. I have all my code debugged and moved over to my production instance, but no matter what I do I keep getting this as an error when I try to validate: 

Methods defined as TestMethod do not support Web service callouts 
Stack Trace: null

I know I need some kind of test class, and through my research I tihnk I can make use of Static Resources to offer salesforce a way to test my code without actually preforming a web service callout. I just dont know how best to proceed. If I upload some sample JSON code into a static resource then make a test class that tests my code, how do I tell salesforce to use the static resource over the actual web service callout? Here is a link to what I plan on using as a recource: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_restful_http_testing_static.htm
 And here is my code:
Wrapper:

public class GDPRWrapper{

    public GDPRWrapper(List<GDPRData> templst){
            GDPRList = templst;
        }
    public List<GDPRData> GDPRList {get; set;}

    public class GDPRData {

        public Integer gdprId {get; set;}  //26636
        public String firstName {get; set;}
        public String lastName {get; set;}
        public String email {get; set;}
        public String phone {get; set;}
        public String accountName {get; set;}
        public String contactId {get; set;}    //AA111222333AAAe
        public String emailHash {get; set;}    //78fcb5ad502033c46d35abcecb3615bd92757fb0451485a19b27b7515f6d82d0
        public String createDate {get; set;}   //2018-05-17T15:19:37.000+0000
        public String responseDate {get; set;} //2018-05-21T10:38:53.000+0000
        public String notifyDate {get; set;}
        public boolean marketing {get; set;}
        public boolean security {get; set;}
        public boolean support {get; set;}
        public boolean contactPhone {get; set;}
        public boolean contactEmail {get; set;}
        public boolean contactOther {get; set;}
        public boolean invalid {get; set;}
        
        
    }
   public static List<GDPRData> parse(httpResponse json){
        return (List<GDPRData>) System.JSON.deserialize(json.getBody(), List<GDPRData>.class);
    }
 
    
}

JSON Parser:

public class JSONDeserialize {

    public GDPRWrapper wrapper {get;set;}
   
    
    @Future(callout=true)
    public static void deserialize() {
        GDPRWrapper wrapper;
    
        
        Http h = new Http();
        HttpRequest request = new HttpRequest();
        
        request.setEndPoint('**********************');
        Blob headerValue = Blob.valueOf('d18849ea4155:d83ce6ef3dbe');
        String authorizationHeader = ('Basic ' + EncodingUtil.base64Encode(headerValue));
        
        
        request.setHeader('Authorization', authorizationHeader);
        request.setMethod('GET');
        try{
        HttpResponse response = h.send(request);
        
        System.debug('JSON RESPONSE: ' + response);
        List<GDPRWrapper.GDPRData> obj = GDPRWrapper.parse(response);
        wrapper = new GDPRWrapper(obj);
        
        System.assert(wrapper.GDPRList!=null);
        updateData(wrapper);
        }catch(JSONException j){
                    System.debug('An unexpected error has occured: ' + j.getMessage());
                }

      }
      
      
      public static void UpdateData(GDPRWrapper wrapper){
        List<Contact> contactPref = new List<Contact>();
        List<Contact> newContacts = new List<Contact>();
          
        for(Integer i = 0; i < wrapper.GDPRList.size(); i ++){
        if(wrapper.GDPRList[i].contactId.length() > 3){
                if(wrapper.GDPRList[i].contactId.subString(0,3) == '003'){
                    Contact toInsert = new Contact();
                    toInsert.firstName = wrapper.GDPRList[i].firstName;
                    toInsert.lastName = wrapper.GDPRList[i].lastName;
                    toInsert.email = wrapper.GDPRList[i].email;
                    toInsert.Email_Hash__c = wrapper.GDPRList[i].emailHash;
                    toInsert.Id = wrapper.GDPRList[i].contactId;
                    toInsert.Sales_and_Marketing__c = wrapper.GDPRList[i].marketing;
                    toInsert.Critical_Security_Notes__c = wrapper.GDPRList[i].security;
                    toInsert.Product_Information__c = wrapper.GDPRList[i].support;
                    toInsert.Contact_Via_Text__c = wrapper.GDPRList[i].contactPhone;
                    toInsert.Contact_Via_Email__c = wrapper.GDPRList[i].contactEmail;
                    contactPref.add(toInsert);
           
                }
            }
        else{
             Contact toInsert = new Contact();
             toInsert.firstName = wrapper.GDPRList[i].firstName;
             toInsert.lastName = wrapper.GDPRList[i].lastName;
             toInsert.email = wrapper.GDPRList[i].email;
             toInsert.Email_Hash__c = wrapper.GDPRList[i].emailHash;
             
             toInsert.Sales_and_Marketing__c = wrapper.GDPRList[i].marketing;
             toInsert.Critical_Security_Notes__c = wrapper.GDPRList[i].security;
             toInsert.Product_Information__c = wrapper.GDPRList[i].support;
             toInsert.Contact_Via_Text__c = wrapper.GDPRList[i].contactPhone;
             toInsert.Contact_Via_Email__c = wrapper.GDPRList[i].contactEmail;
             newContacts.add(toInsert);
        
        
        }
           
            
          
        
        }
          try{
              if(contactPref.size()>0){
                  upsert contactPref;
              }
              if(NewContacts.size()>0){
                  insert NewContacts;
              }          
            } 
            catch(DmlException e){
                    System.debug('An unexpected error has occured: ' + e.getMessage());
                }
      
      }
     }

My main question is this: How do I modify my desearialize method so that I can make use of a static resource for testing purposes?