Unit testing JavaFx 2 application with TestNG

Question

I wrote a rather complex JavaFx 2 application for which I'd like to write a bunch of unit tests. Problem is when I try to conduct the tests I get a runtime error complaining about uninitialized toolkit.

From what I can tell I should somehow invoke Application.launch() in a @BeforeClass method but this causes a deadlock as Application.launch() doesn't return to calling thread.

So question is how should I initialize JavaFx?

This is the skeleton of the code that doesn't work:

public class AppTest extends Application {

    @BeforeClass
    public void initialize() {
        launch(); //this causes a deadlock
    }

    @Test
    public void test1() {
        //conduct test here
    }

    @Test
    public void test2() {
        //conduct other test here
    }

    @Override
    public void start(Stage arg0) throws Exception {
    }

Thanks in advance!

You may also want to look at the [JemmyFX visual testing framework](http://fxexperience.com/2012/02/announcing-jemmyfx/) which the JavaFX team use to test their software. — jewelsea, Nov 21 '12 at 08:15
Better address for JemmyFX: http://jemmy.java.net/JemmyFXGuide/jemmy-guide.html — assylias, Aug 10 '13 at 20:20

score 3 · Accepted Answer · edited May 23 '17 at 10:28

From another question here on stackoverflow, I've made myself this little helper class:

import javafx.application.Application;
import javafx.stage.Stage;

public class JavaFXInitializer extends Application {

    private static Object barrier = new Object();

    @Override
    public void start(Stage primaryStage) throws Exception {
        synchronized(barrier) {
            barrier.notify();
        }
    }

    public static void initialize() throws InterruptedException {
        Thread t = new Thread("JavaFX Init Thread") {
            public void run() {
                Application.launch(JavaFXInitializer.class, new String[0]);
            }
        };
        t.setDaemon(true);
        t.start();      
        synchronized(barrier) {
            barrier.wait();
        }
    }
}

which can then be used easily in a @BeforeClass setup method:

@BeforeClass
public void setup() throws InterruptedException {
    JavaFXInitializer.initialize();
}

This is very similar to the solution I came up with :) – Athelionas Aug 28 '15 at 09:00 — Athelionas, Aug 28 '15 at 09:00

score 1 · Answer 2 · answered May 16 '13 at 12:41

The main think is to consider your tests to be run inside an FX thread. When you create a class extends Application, you create in fact a process. This is what you want to test.

So to launch some unit tests on an Application, first create an FXAppTest that extends Application and then inside FXAppTest you launch your unit test. Here is the idea.

Here is an example with JUnit. I create a Runner that launch the test inside an FXApp for test. Here is an example of code for FxApplicationTest (we launch unit test inside it)

 public class FxApplicationTest extends Application {

    private volatile boolean isStopped;

    @Override
    public void start(final Stage stage) {
        StackPane root = new StackPane();
        Scene scene = new Scene(root, 10, 10);
        stage.setScene(scene);
    }

    public void startApp() {
        launch();
    }

    public void execute(final BlockJUnit4ClassRunner runner, final RunNotifier notifier) throws InterruptedException {
        isStopped = false;
        Platform.runLater(new Runnable() {
            @Override
            public void run() {
                runner.run(notifier);
                isStopped = true;
            }
        });
        while (!isStopped) {
            Thread.sleep(100);
        }
    }

And the Runner :

import org.apache.log4j.Logger;
import org.junit.runner.Description;
import org.junit.runner.Runner;
import org.junit.runner.notification.RunNotifier;
import org.junit.runners.BlockJUnit4ClassRunner;
import org.junit.runners.model.InitializationError;

public class JUnitFxRunner extends Runner {

    private final BlockJUnit4ClassRunner runner;
    private final Logger LOGGER = Logger.getLogger(JUnitFxRunner.class);

    public JUnitFxRunner(final Class<?> klass) throws InitializationError {
        super();
        runner = new BlockJUnit4ClassRunner(klass);
    }

    @Override
    public Description getDescription() {
        return Description.EMPTY;
    }

    @Override
    public void run(final RunNotifier notifier) {
        try {

            final FxApplicationTest fxApplicationTest = new FxApplicationTest();

            MyTestRunner runnable = new MyTestRunner(runner, notifier, fxApplicationTest);
            new Thread(runnable).start();
            Thread.sleep(100);
            runnable.execute();
        } catch (Exception e) {
            LOGGER.error(e.getMessage(), e);
        }

    }

    private class MyTestRunner implements Runnable {

        private final BlockJUnit4ClassRunner runner;
        private final RunNotifier notifier;
        private final FxApplicationTest fxApp;

        public MyTestRunner(final BlockJUnit4ClassRunner runner, final RunNotifier notifier, final FxApplicationTest fxApp) {
            this.runner = runner;
            this.notifier = notifier;
            this.fxApp = fxApp;
        }

        @Override
        public void run() {
            fxApp.startApp();
        }

        public void execute() throws InterruptedException {
            fxApp.execute(runner, notifier);
        }
    }

}

Now, simply launch test using the runner :

import fr.samarie_projects.fx.utils.JUnitFxRunner;

@RunWith(JUnitFxRunner.class)
public class MainFxAppTest {

    @org.junit.Test
    public void testName() throws Exception {
        MainFxApp fxApp = new MainFxApp();
        fxApp.start(new Stage());
    }

}

This unit test MainFxApp

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

public class MainFxApp extends Application {

    @Override
    public void start(final Stage stage) throws Exception {
        StackPane root = new StackPane();
        Scene scene = new Scene(root, 10, 10);
        stage.setScene(scene);
    }

    public static void main(final String[] args) {
        launch(args);
    }

}

Sure, this code need to be reviewed. It is only to present the idea.

score 0 · Answer 3 · answered Nov 20 '12 at 21:10

Well, considering that you might have your JavaFX app located at project-root/src/main/java/package/FXApp.java then you might have your tests located elsewhere like project-root/src/test/java/package/FXAppTest.java . This being the case, the FXAppTest class could call the FXApp class by initializing it using BeforeClass .

In theory you should be able to start your FX app with something like:

// imports located here that import junit 4.11+ packages (or TestNG)
public class FXAppTest {
@BeforeClass
public void initialize() {
   FXApp fxa = new FXApp();
   while ( fxa.isLoading() ) {
      // do nothing
   }
}
....

NOTE: Notice that FXAppTest does not extend Application here.

Now, if this doesn't clue you into the problem, you could enable JMX args on the JVM and then view the locked threads with JVisualVM.

Unit testing JavaFx 2 application with TestNG

3 Answers3

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