How to set 'headless' property in a Spring Boot test?

Question

I am testing using Spring Boot with JavaFX (Based on some excellent YouTube videos that explain this).

To make it work with TestFX, I need to create the context like this:

@Override
public void init() throws Exception {
    SpringApplicationBuilder builder = new SpringApplicationBuilder(MyJavaFXApplication.class);
    builder.headless(false); // Needed for TestFX
    context = builder.run(getParameters().getRaw().stream().toArray(String[]::new));

    FXMLLoader loader = new FXMLLoader(getClass().getResource("main.fxml"));
    loader.setControllerFactory(context::getBean);
    rootNode = loader.load();
}

I now want to test this JavaFX application, for this I use:

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE)
public class MyJavaFXApplicationUITest extends TestFXBase {

    @MockBean
    private MachineService machineService;

    @Test
    public void test() throws InterruptedException {
        WaitForAsyncUtils.waitForFxEvents();
        verifyThat("#statusText", (Text text ) -> text.getText().equals("Machine stopped"));
        clickOn("#startMachineButton");
        verifyThat("#startMachineButton", Node::isDisabled);
        verifyThat("#statusText", (Text text ) -> text.getText().equals("Machine started"));
    }
}

This starts a Spring context and replaces the "normal" beans with the mock beans as expected.

However, I now get a java.awt.HeadlessException because this 'headless' property is not set to false like is done during normal startup. How to I set this property during the test?

EDIT:

Looking closer it seems that there are 2 context started, one that the Spring testing framework starts and the one I create manually in the init method, so the application under test is not using the mocked beans. If somebody would have a clue how to get the test context reference in the init() method, I would be very happy.

Answer 1

The @SpringBootTest uses SpringBootContextLoader class as context loader, so the ApplicationContext is load from the method SpringBootContextLoader.loadContext as this:

SpringApplication application = getSpringApplication();
......
return application.run();

When invoke the method application.run(), application configure the system headless property with it's internal headless property.

So, If we want to set 'headless' property in a Spring Boot test, just create a customize specific ContextLoader class extends SpringBootContextLoader class, and override the method getSpringApplication with set the headless property as false, then assign the specific ContextLoader with annotation @ContextConfiguration for @SpringBootTest. The code:

public class HeadlessSpringBootContextLoader extends SpringBootContextLoader {
    @Override
    protected SpringApplication getSpringApplication() {
        SpringApplication application = super.getSpringApplication();
        application.setHeadless(false);
        return application;
    }
}

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment=SpringBootTest.WebEnvironment.NONE)
@ContextConfiguration(loader = HeadlessSpringBootContextLoader.class)
public class ApplicationTests {

    @Test
    public void contextLoads() {

    }

}

Answer 2

The comment from Praveen Kumar pointed in the good direction. When I run the test with -Djava.awt.headless=false, then there is no exception.

To solve the other problem of the 2 Spring contexts, I had to do the following:

Suppose this is your main JavaFx startup class:

    @SpringBootApplication
    public class MyJavaFXClientApplication extends Application {

    private ConfigurableApplicationContext context;
    private Parent rootNode;

    @Override
    public void init() throws Exception {
        SpringApplicationBuilder builder = new SpringApplicationBuilder(MyJavaFXClientApplication.class);
        builder.headless(false); // Needed for TestFX
        context = builder.run(getParameters().getRaw().stream().toArray(String[]::new));

        FXMLLoader loader = new FXMLLoader(getClass().getResource("main.fxml"));
        loader.setControllerFactory(context::getBean);
        rootNode = loader.load();
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        Rectangle2D visualBounds = Screen.getPrimary().getVisualBounds();
        double width = visualBounds.getWidth();
        double height = visualBounds.getHeight();

        primaryStage.setScene(new Scene(rootNode, width, height));
        primaryStage.centerOnScreen();
        primaryStage.show();
    }

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

    @Override
    public void stop() throws Exception {
        context.close();
    }

    public void setContext(ConfigurableApplicationContext context) {
        this.context = context;
    }
}

And for testing, you use this abstract base class (Courtesy of this YouTube video by MVP Java):

public abstract class TestFXBase extends ApplicationTest {

    @BeforeClass
    public static void setupHeadlessMode() {
        if (Boolean.getBoolean("headless")) {
            System.setProperty("testfx.robot", "glass");
            System.setProperty("testfx.headless", "true");
            System.setProperty("prism.order", "sw");
            System.setProperty("prism.text", "t2k");
            System.setProperty("java.awt.headless", "true");
        }
    }

    @After
    public void afterEachTest() throws TimeoutException {
        FxToolkit.hideStage();
        release(new KeyCode[0]);
        release(new MouseButton[0]);
    }

    @SuppressWarnings("unchecked")
    public <T extends Node> T find(String query, Class<T> clazz) {
        return (T) lookup(query).queryAll().iterator().next();
    }
}

Then you can write a test like this:

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE)
public class MyJavaFXApplicationUITest extends TestFXBase {

    @MockBean
    private TemperatureService temperatureService;

    @Autowired
    private ConfigurableApplicationContext context;

    @Override
    public void start(Stage stage) throws Exception {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("main.fxml"));
        loader.setControllerFactory(context::getBean);
        Parent rootNode = loader.load();

        stage.setScene(new Scene(rootNode, 800, 600));
        stage.centerOnScreen();
        stage.show();
    }

    @Test
    public void testTemperatureReading() throws InterruptedException {
        when(temperatureService.getCurrentTemperature()).thenReturn(new Temperature(25.0));
        WaitForAsyncUtils.waitForFxEvents();

        assertThat(find("#temperatureText", Text.class).getText()).isEqualTo("25.00 C");
    }
}

This allows to start the UI using mock services.