created test for setting new highscore

src/test/java/Gui/GameGuiTest.java

@@ -20,6 +20,7 @@ class GameGuiTest {
 	void setUp(){
 	    Gui.StartMainMenu();
 	    gameGui.createGui();
+	    gameGui.createLosingPanel();
 	}
 
 	@Test
@@ -31,4 +32,13 @@ class GameGuiTest {
 	    assertEquals(new Insets(10, 10, 10, 10), gameGui.gbc.insets);
 	}
 
+	@Test
+    public void testHighScoreChange() {
+        int expectedHighScore = 7;
+		gameGui.highScore = 0;
+        gameGui.questionNr = 7;
+        gameGui.highScore();
+        assertEquals(expectedHighScore, gameGui.highScore);
+    }
+	
 }