Hello I want to use a static resource for my Mock but I cannot get it to work where am I going wrong based on this snippet of code:
 

@isTest
global class TrelloAPICalloutClass_Mock implements HttpCalloutMock {

    public static HttpResponse res;
    public static HttpRequest req;
    private String whichMock;

    public TrelloAPICalloutClass_Mock (String mockNeeded){
        this.whichMock = mockNeeded;
    }

    global HTTPResponse respond(HTTPRequest req){
        res = new HttpResponse();
        switch on whichMock {
            when 'createboards' {
                createBoardMock();
            }
            when 'getattachment' {
                attachmentMock();
            }
            when 'gettrelloboards' {
                getTrelloBoardsMock();
            }
            when 'getTrelloListsFromBoardMock' {
                getTrelloListsFromBoardMock();
            }
            when 'getTrelloLabelsFromBoardsMock' {
                getTrelloLabelsFromBoardsMock();
            }
            when 'getTrelloBoardsMockError' {
                getTrelloBoardsMockError();
            }
            when 'getTrelloBoardsMockNewBoard' {
                getTrelloBoardsMockNewBoard();
            }
            when 'getTrelloBoardsMockUpdateName' {
                getTrelloBoardsMockUpdateName();
            }
            when 'getTrelloListsFromBoardMockNewList' {
                getTrelloListsFromBoardMockNewList();
            }
        }
        return res;        
        
    }

    private static void getTrelloBoardsMock(){
        // Get The Trello Boards
        StaticResourceCalloutMock mock = new StaticResourceCalloutMock();
        mock.setStaticResource('getOrgBoards');
        mock.setHeader('Content-Type', 'application/json');
        mock.setStatusCode(200);
        Test.setMock(HttpCalloutMock.class, mock);
    }

I have no doubt it is to do with the res vs the mock but I cannot work out the issue