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A Junit @rule for running tests on the JavaFX thread
import java.util.concurrent.CountDownLatch;
import javax.swing.SwingUtilities;
import javafx.application.Platform;
import javafx.embed.swing.JFXPanel;
import org.junit.Rule;
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;
/**
* A JUnit {@link Rule} for running tests on the JavaFX thread and performing
* JavaFX initialisation. To include in your test case, add the following code:
*
* <pre>
* {@literal @}Rule
* public JavaFXThreadingRule jfxRule = new JavaFXThreadingRule();
* </pre>
*
* @author Andy Till
*
*/
public class JavaFXThreadingRule implements TestRule {
/**
* Flag for setting up the JavaFX, we only need to do this once for all tests.
*/
private static boolean jfxIsSetup;
@Override
public Statement apply(Statement statement, Description description) {
return new OnJFXThreadStatement(statement);
}
private static class OnJFXThreadStatement extends Statement {
private final Statement statement;
public OnJFXThreadStatement(Statement aStatement) {
statement = aStatement;
}
private Throwable rethrownException = null;
@Override
public void evaluate() throws Throwable {
if(!jfxIsSetup) {
setupJavaFX();
jfxIsSetup = true;
}
final CountDownLatch countDownLatch = new CountDownLatch(1);
Platform.runLater(new Runnable() {
@Override
public void run() {
try {
statement.evaluate();
} catch (Throwable e) {
rethrownException = e;
}
countDownLatch.countDown();
}});
countDownLatch.await();
// if an exception was thrown by the statement during evaluation,
// then re-throw it to fail the test
if(rethrownException != null) {
throw rethrownException;
}
}
protected void setupJavaFX() throws InterruptedException {
long timeMillis = System.currentTimeMillis();
final CountDownLatch latch = new CountDownLatch(1);
SwingUtilities.invokeLater(new Runnable() {
public void run() {
// initializes JavaFX environment
new JFXPanel();
latch.countDown();
}
});
System.out.println("javafx initialising...");
latch.await();
System.out.println("javafx is initialised in " + (System.currentTimeMillis() - timeMillis) + "ms");
}
}
}
@mkarg

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commented Aug 13, 2016

Unfortunately does not work with @Test(timeout = ...) because JUnit apparently spans a new thread within baseStatement.evaluate(); ;-(

@NottmTony

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commented Nov 30, 2016

Cheers for this ... worked a treat.

@dawidsamolyk

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commented Feb 3, 2017

In my opinion you should invoke countDownLatch.countDown(); in finally clause.
countDownLatch.await(); could be also dangerous. It would be better to use some timeout.

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