JavaFXThreadingRule.java

package com.shootoff.gui;

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
 *         (http://andrewtill.blogspot.com/2012/10/junit-rule-for-javafx-
 *         controller-testing.html)
 * 
 */
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 {
			final CountDownLatch latch = new CountDownLatch(1);

			SwingUtilities.invokeLater(new Runnable() {
				public void run() {
					// initializes JavaFX environment
					new JFXPanel();

					latch.countDown();
				}
			});

			latch.await();
		}

	}
}