Creating Unit Tests For class that uses resources c# / VisualStudio

I have quite a problem with creating tests for class that uses resources.

Outline of class:

class CardInfo     
 private readonly Dictionary<int, Card> Cards= new Dictionary<int, Card>
        {
            [(int)Card.Fireball] = new Card(CardCode.Fireball, ResourceService.MESSAGE_CARD_TITLE_FIREBALL, ResourceService.MESSAGE_CARD_DESCRIPTION_FIREBALL),
    };

Method i'm trying to test:

public Card getCard(int CardCode) => Cards.ContainsKey(CardCode) ? Cards[CardCode] : new Card(CardCode.NOTSPECIFED, ResourceService.MESSAGE_INTERNAL_ERROR_TITLE_CARDNOTEXISTENT, ResourceService.MESSAGE_INTERNAL_ERROR_BODY_CARDNOTEXISTENT);

In test project i had tried:

  [TestMethod]
        public  async Task getInternalServerResponseErrorUnknownTest()
        {
           await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal,
() =>
{
cardService = new CardInfo();
});

currently error is thrown here, "ResourceMap not found"

in ResourceService:

    public static string MESSAGE_CARD_TITLE_FIREBALL
    {
        get
        {
            return resourceLoader.GetString("MESSAGE_CARD_TITLE_FIREBALL");
        }
    }

How could i fix this?