Simple TestFX example fails

Question

Working with TestFX 4.0.14 in Eclipse photon and fx9 or fx11 (doesn't matter), the simple example test from the TestFX wiki fails in should_click_on_button() with

Expected: Labeled has text "clicked!"
         but: was "click me!"

When looking at the screen, the pane and its contained button is shown, but the mouse moves to someplace else: so the button is never clicked and consequently its text never changed.

Any idea what's wrong/how to fix?

The test code (all copied from the wiki for convenience):

import org.junit.Test;
import org.testfx.framework.junit.ApplicationTest;

import static org.testfx.api.FxAssert.*;
import static org.testfx.matcher.control.LabeledMatchers.*;

import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

/**
 * Simple testfx example from testfx wiki:
 * https://github.com/TestFX/TestFX/wiki/Getting-Started
 * 
 */
public class ClickApplicationTest extends ApplicationTest {
    @Override
    public void start(Stage stage) {
        Parent sceneRoot = new ClickApplication.ClickPane();
        Scene scene = new Scene(sceneRoot, 100, 100);
        stage.setScene(scene);
        stage.show();
    }

    @Test
    public void should_contain_button() {
        // expect:
        verifyThat(".button", hasText("click me!"));
    }

    @Test
    public void should_click_on_button() {
        // when:
        clickOn(".button");

        // then:
        verifyThat(".button", hasText("clicked!"));
    }


}

The application code:

import javafx.application.Application;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

/**
 * Simple testfx example from testfx wiki:
 * https://github.com/TestFX/TestFX/wiki/Getting-Started
 * 
 */
public class ClickApplication extends Application {
    // application for acceptance tests.
    @Override public void start(Stage stage) {
        Parent sceneRoot = new ClickPane();
        Scene scene = new Scene(sceneRoot, 100, 100);
        stage.setScene(scene);
        stage.show();
    }

    // scene object for unit tests
    public static class ClickPane extends StackPane {
        public ClickPane() {
            super();
            Button button = new Button("click me!");
            button.setOnAction(actionEvent -> button.setText("clicked!"));
            getChildren().add(button);
        }
    }
}

---

Update:

Found an open issue in TestFX that might match. It mentions a core fx bug that might be the reason - but doesn't seem to be: it's fixed in fx11 (verified that the code in the core bug report passes), but the testfx issue prevails ..

Answer 1

Turned out to be a problem with several reasons:

• at the very base is a core bug - robot doesn't move correctly on win (10 only?) HiDPI screens, so not everybody experiences the failure
• the core bug is fixed in fx11 (in native win code), so that the now public fx Robot behaves well
• TestFX robot-related code in the latest release (4.0.14) is not yet updated to fx11, the repo version is
• by default, TestFX uses the AWTRobot which still fails (at least in the context of TestFX, the example in the core bug report passes)
• to make TestFX tests run reliable on win HiDPI screens, we need to force the usage of the fx robot, done by setting a system property testfx.robot to glass
• one last quirk: when setting the property programmatically via System.getProperties().put("testfx.robot", "glass") in the testing code, it is mandatory to do this before the tests class starts, that is in a method annotated by @BeforeClass (not in @Before nor testApp.init())! Otherwise the very first test that directly or indirectly involves a mouseMove will fail, subsequent ones are fine (puzzled me a while because the failure feels spurious;).

Sample:

public class ClickTest extends ApplicationTest {

    @Test
    public void testClick() {
        verifyThat(".button", hasText("click me!"));
        clickOn(".button");
        verifyThat(".button", hasText("clicked!"));
    }

    /**
     * Use glass robot.
     * Note: this must happen once before the class is loaded. Otherwise,
     * the very first test run uses the awt robot
     */
    @BeforeClass
    public static void config() throws Exception {
        System.getProperties().put("testfx.robot", "glass");
    }

    @Override
    public void start(Stage stage) {
        Parent sceneRoot = new ClickPane();
        Scene scene = new Scene(sceneRoot, 100, 100);
        stage.setScene(scene);
        stage.show();
    }

    // scene object for unit tests
    public static class ClickPane extends StackPane {
        public ClickPane() {
            super();
            Button button = new Button("click me!");
            button.setOnAction(actionEvent -> button.setText("clicked!"));
            getChildren().add(button);
        }
    }

    @SuppressWarnings("unused")
    private static final Logger LOG = Logger
            .getLogger(ClickTest.class.getName());
}