ExceptionInInitializerError while JUnit testing

Hello I am testing method createReservation from the model

@org.junit.jupiter.api.Test
  void createReservation() {
    modelManager.createReservation(new Reservation(new Item(1232,"title","author",2002,new MyDate(12,07,2021),"comment") {
      public String toString() {
        return null;
      }
    },"firstname","lastname","test@test.com",true,new MyDate(12,07,2023),new MyDate(24,07,2023)));
    Reservation reservation= modelManager.getReservations().get(0);
    assertEquals(new MyDate(),reservation.getStartDate());
  }

I keep getting this error:

java.lang.ExceptionInInitializerError
    at javafx.controls/javafx.scene.control.DialogPane.createContentLabel(DialogPane.java:167)
    at javafx.controls/javafx.scene.control.DialogPane.<init>(DialogPane.java:218)
    at javafx.controls/javafx.scene.control.Dialog.<init>(Dialog.java:512)
    at javafx.controls/javafx.scene.control.Alert.<init>(Alert.java:247)
    at javafx.controls/javafx.scene.control.Alert.<init>(Alert.java:222)
    at FairyTaleLib/com.sep1re.fairytalelib.model.LibModelManager.<init>(LibModelManager.java:64)
    at FairyTaleLib/com.sep1re.fairytalelib.model.LibModelManagerTest.setUp(LibModelManagerTest.java:22)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
Caused by: java.lang.IllegalStateException: Toolkit not initialized

This is how i initialized the model(dont mind the arraylist):

  private ArrayList<Item> items;
  private LibModelManager modelManager;
  @org.junit.jupiter.api.BeforeEach void setUp()
  {
    items=new ArrayList();
    modelManager= new LibModelManager();
  }