JUnit testing a method with JOptionPane.showMessageDialog

I have made a game where a user and an AI takes turns "rolling" a dice. The game automatically takes the AI's turn and returns to the user's turn. I used JOptionPane.showMessageDialog to popup a dialog box notifying the user that it is their turn. So all this is working properly but when I execute a JUnit test class to test the hold() method the popup comes up. Is there a way to suppress the popup or automatically close the window in a JUnit Test class?

    public void hold() {

    this.swapWhoseTurn();           
    this.setChanged();
    this.notifyObservers();

    if (this.getCurrentPlayer().getIsMyTurn() == this.getComputerPlayer().getIsMyTurn()) {
        this.theComputer.takeTurn();
        this.hold();
        HumanPlayerPanel.turnAlert();
    }

The turnAlert is a static method in another class called HumanPlayerPanel. Here is the code.

    public static void turnAlert() {
    JOptionPane.showMessageDialog(null, "It is your turn");
    }

I saw that I can call doClick method on the OK_Option button but I'm not too sure how to find that button. Any help is appreciated.