### Question:
SpoonCodeInstrument extends JfxInstrument implements Initializable { void cleanPropertiesPanel() { propPanel.getChildren().clear(); }  @Override void initialize(final URL url, final ResourceBundle res);  }### Answer:
@Test void testCleanPropertiesPanel(final FxRobot robot) { final VBox propsPanel = robot.lookup("#propPanel").query(); final CtElement stub = Mockito.mock(CtElement.class); Platform.runLater(() -> spoonCodeInstrument.updatePropertiesPanel(stub)); WaitForAsyncUtils.waitForFxEvents(); Platform.runLater(() -> spoonCodeInstrument.cleanPropertiesPanel()); WaitForAsyncUtils.waitForFxEvents(); assertThat(propsPanel.getChildren()).isEmpty(); }