如何使用JUnit单元测试JavaFX控制器

Question

初始化JavaFX运行时的正确方法是什么，以便您可以对使用并发工具和的控制器进行单元测试（使用JUnit）Platform.runLater(Runnable)？

Application.launch(...)从该@BeforeClass方法调用会导致死锁。如果Application.launch(...)未调用，则会引发以下错误：

java.lang.IllegalStateException: Toolkit not initialized
    at com.sun.javafx.application.PlatformImpl.runLater(PlatformImpl.java:121)
    at com.sun.javafx.application.PlatformImpl.runLater(PlatformImpl.java:116)
    at javafx.application.Platform.runLater(Platform.java:52)
    at javafx.concurrent.Task.runLater(Task.java:1042)
    at javafx.concurrent.Task.updateMessage(Task.java:987)
    at com.xyz.AudioSegmentExtractor.call(AudioSegmentExtractor.java:64)
    at com.xyz.CompletionControllerTest.setUp(CompletionControllerTest.java:69)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:27)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

后续：这是我根据@SergeyGrinev的建议一直使用的主题。

... // Inside test class

public static class AsNonApp extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {
        // noop
    }
}

@BeforeClass
public static void initJFX() {
    Thread t = new Thread("JavaFX Init Thread") {
        public void run() {
            Application.launch(AsNonApp.class, new String[0]);
        }
    };
    t.setDaemon(true);
    t.start();
}
... // controller tests follow...

Answer 1

调用launch()由@BeforeClass是正确的做法。请注意，launch()这不会将控制权返回给调用代码。因此，您必须将其包装到中new Thread(...).start()。

7年后的更新：

使用TestFX！它将以适当的方式进行启动。例如，您可以从TestFX的ApplicaionTest类扩展测试，并使用相同的代码：

public class MyTest extends ApplicationTest {

@Override
public void start (Stage stage) throws Exception {
    FXMLLoader loader = new FXMLLoader(
            getClass().getResource("mypage.fxml"));
    stage.setScene(scene = new Scene(loader.load(), 300, 300));
    stage.show();
}

并编写如下测试：

@Test
public void testBlueHasOnlyOneEntry() {
    clickOn("#tfSearch").write("blue");
    verifyThat("#labelCount", hasText("1"));
}