Simplify Zest tests by using the SWTBot

This removes classes such as the WidgetVisitor in favor of using the
methods provided by the SWTBot. Note that because the SWTBot doesn't
understand the Zest model, the tests still have to be executed in the UI
thread.

org.eclipse.zest.tests/META-INF/MANIFEST.MF

@@ -3,6 +3,7 @@ Bundle-ManifestVersion: 2
 Bundle-Name: Graphical Editing Framework Zest Tests
 Bundle-SymbolicName: org.eclipse.zest.tests;singleton:=true
 Bundle-Version: 1.8.600.qualifier
+Import-Package: org.slf4j;version="1.7.30"
 Require-Bundle: org.eclipse.ui,
  org.eclipse.core.runtime,
  org.eclipse.pde,
@@ -14,7 +15,8 @@ Require-Bundle: org.eclipse.ui,
  org.eclipse.zest.core,
  org.eclipse.zest.examples,
  org.eclipse.zest.layouts,
- org.junit
+ org.junit,
+ org.eclipse.swtbot.swt.finder;bundle-version="4.2.1"
 Bundle-ActivationPolicy: lazy
 Bundle-RequiredExecutionEnvironment: JavaSE-17
 Automatic-Module-Name: org.eclipse.zest.tests

org.eclipse.zest.tests/src/org/eclipse/zest/tests/examples/AbstractGraphTest.java

@@ -26,14 +26,9 @@
 import java.util.Objects;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.atomic.AtomicReference;
-import java.util.function.Predicate;
 
-import org.eclipse.swt.widgets.Button;
-import org.eclipse.swt.widgets.Canvas;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Shell;
-import org.eclipse.swt.widgets.Text;
-import org.eclipse.swt.widgets.Widget;
 
 import org.eclipse.core.runtime.Assert;
 import org.eclipse.zest.core.widgets.Graph;
@@ -51,7 +46,6 @@
 import org.eclipse.zest.layouts.dataStructures.InternalRelationship;
 import org.eclipse.zest.tests.utils.GraphicalRobot;
 import org.eclipse.zest.tests.utils.Snippet;
-import org.eclipse.zest.tests.utils.WidgetVisitor;
 
 import org.eclipse.draw2d.EventDispatcher;
 import org.eclipse.draw2d.IFigure;
@@ -381,52 +375,6 @@ protected static void assertInstanceOf(Object object, Class<?> clazz) {
 		assertTrue(clazz.isAssignableFrom(object.getClass()));
 	}
 
-	/**
-	 * @return the {@link Button} with given text.
-	 */
-	protected static Button findButtonByName(Shell shell, String text) {
-		return findWidget(shell, Button.class, b -> text.equals(b.getText()));
-	}
-
-	/**
-	 * @return the first {@link Text} in the given {@link Shell}.
-	 */
-	protected static Text findText(Shell shell) {
-		return findWidget(shell, Text.class, t -> true);
-	}
-
-	/**
-	 * @return the first {@link Canvas} in the given {@link Shell}.
-	 */
-	protected static Canvas findCanvas(Shell shell) {
-		return findWidget(shell, Canvas.class, t -> true);
-	}
-
-	/**
-	 * Convenience method for finding a given {@link Widget} in a {@link Shell}.
-	 * type.
-	 *
-	 * @return The first widget of type {@code T}, matching the predicate. Returns
-	 *         {@code null} if no such widget is found.
-	 */
-	private static <T extends Widget> T findWidget(Shell shell, Class<T> clazz, Predicate<T> predicate) {
-		AtomicReference<T> ref = new AtomicReference<>();
-		new WidgetVisitor() {
-			@Override
-			public boolean visit(Widget w) {
-				if (clazz.isAssignableFrom(w.getClass())) {
-					T widget = clazz.cast(w);
-					if (predicate.test(widget)) {
-						ref.set(widget);
-						return false;
-					}
-				}
-				return true;
-			}
-		}.traverse(shell);
-		return ref.get();
-	}
-
 	/**
 	 * Pumps the event loop for the given number of milliseconds. At least one
 	 * events loop will be executed.
@@ -435,7 +383,7 @@ protected static void waitEventLoop(int time) {
 		long start = System.currentTimeMillis();
 		do {
 			while (Display.getCurrent().readAndDispatch()) {
-				// do nothing
+				Thread.yield();
 			}
 		} while (System.currentTimeMillis() - start < time);
 	}

org.eclipse.zest.tests/src/org/eclipse/zest/tests/examples/GraphJFaceTests.java

@@ -19,8 +19,6 @@
 import java.lang.invoke.VarHandle;
 import java.util.concurrent.atomic.AtomicReference;
 
-import org.eclipse.swt.widgets.Button;
-
 import org.eclipse.jface.viewers.IStructuredSelection;
 import org.eclipse.jface.viewers.LabelProvider;
 import org.eclipse.zest.core.viewers.GraphViewer;
@@ -175,8 +173,7 @@ public void testGraphJFaceSnippet5() {
 		assertEquals(graph.getConnections().size(), 3);
 		assertEquals(graph.getNodes().size(), 3);
 
-		Button refresh = findButtonByName(graph.getShell(), "Refresh");
-		robot.select(refresh);
+		robot.button("Refresh").click();
 
 		assertConnection(graph.getConnections().get(0), "Paper", "Rock");
 		assertConnection(graph.getConnections().get(1), "Scissors", "Paper");

org.eclipse.zest.tests/src/org/eclipse/zest/tests/examples/GraphSWTTests.java

@@ -31,12 +31,14 @@
 import org.eclipse.swt.graphics.ImageData;
 import org.eclipse.swt.graphics.RGB;
 import org.eclipse.swt.graphics.Rectangle;
-import org.eclipse.swt.widgets.Button;
 import org.eclipse.swt.widgets.Canvas;
 import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Event;
 import org.eclipse.swt.widgets.Shell;
-import org.eclipse.swt.widgets.Text;
 
+import org.eclipse.swtbot.swt.finder.SWTBot;
+import org.eclipse.swtbot.swt.finder.widgets.SWTBotButton;
+import org.eclipse.swtbot.swt.finder.widgets.SWTBotText;
 import org.eclipse.zest.core.widgets.Graph;
 import org.eclipse.zest.core.widgets.GraphConnection;
 import org.eclipse.zest.core.widgets.GraphContainer;
@@ -116,8 +118,7 @@ public void testAnimationSnippet() {
 		AtomicInteger repaintCount = new AtomicInteger();
 		graph.addPaintListener(event -> repaintCount.incrementAndGet());
 
-		Button button = findButtonByName(graph.getShell(), "Animate");
-		robot.select(button);
+		robot.button("Animate").click();
 
 		assertTrue("Animation was likely not drawn!", repaintCount.get() > 0);
 		assertNoOverlap(graph);
@@ -172,22 +173,23 @@ public void testGraphSnippet1() {
 
 			// The NodeSearchDialog should now be active
 			dialogShell = graph.getDisplay().getActiveShell();
-			Text text = findText(dialogShell);
-			Button next = findButtonByName(dialogShell, "Next");
+			SWTBot dialogRobot = new SWTBot(dialogShell);
+			SWTBotText textRobot = dialogRobot.text();
+			SWTBotButton buttonRobot = dialogRobot.button("Next");
 
-			text.setText("Paper");
-			robot.focusOut(text);
-			robot.select(next);
+			textRobot.setText("Paper");
+			focusOut(textRobot);
+			buttonRobot.click();
 			assertEquals(graph.getSelection(), List.of(node1));
 
-			text.setText("Rock");
-			robot.focusOut(text);
-			robot.select(next);
+			textRobot.setText("Rock");
+			focusOut(textRobot);
+			buttonRobot.click();
 			assertEquals(graph.getSelection(), List.of(node2));
 
-			text.setText("Scissor");
-			robot.focusOut(text);
-			robot.select(next);
+			textRobot.setText("Scissors");
+			focusOut(textRobot);
+			buttonRobot.click();
 			assertEquals(graph.getSelection(), List.of(node3));
 		} finally {
 			if (dialogShell != null) {
@@ -196,6 +198,16 @@ public void testGraphSnippet1() {
 		}
 	}
 
+	/**
+	 * This method simulates a {@link SWT#FocusOut} event using the given
+	 * {@code widget}. Events are sent to the argument.
+	 *
+	 * @param widget The widget whose focus has been lost.
+	 */
+	private static void focusOut(SWTBotText robot) {
+		robot.widget.notifyListeners(SWT.FocusOut, new Event());
+	}
+
 	/**
 	 * Tests whether images are properly handled.
 	 */
@@ -418,10 +430,9 @@ public void testGraphSnippet10() {
 		assertConnection(connection2, "Rock", "Scissors");
 		assertConnection(connection3, "Scissors", "Paper");
 
-		Button button = findButtonByName(graph.getShell(), "Change Curve");
 		for (int i = 0; i < 4; ++i) {
 			if (i > 0) {
-				robot.select(button);
+				robot.button("Change Curve").click();
 			}
 			// Old connection is removed and a new one is added
 			assertArc(graph.getConnections().get(2), i * 10 /* ° */);
@@ -692,12 +703,12 @@ public void testPaintSnippet() {
 		graph.selectAll();
 		waitEventLoop(0);
 
-		Button button = findButtonByName(graph.getShell(), "Take Screenshot");
-		robot.select(button);
+		robot.button("Take Screenshot").click();
 		waitEventLoop(0);
 
 		Shell popupShell = graph.getDisplay().getActiveShell();
-		Canvas popupCanvas = findCanvas(popupShell);
+		SWTBot popupRobot = new SWTBot(popupShell);
+		Canvas popupCanvas = popupRobot.canvas().widget;
 		Rectangle bounds = popupCanvas.getBounds();
 
 		GC gc = new GC(popupCanvas);

org.eclipse.zest.tests/src/org/eclipse/zest/tests/utils/GraphicalRobot.java

@@ -15,9 +15,9 @@
 
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.widgets.Event;
-import org.eclipse.swt.widgets.Widget;
 
 import org.eclipse.core.runtime.Assert;
+import org.eclipse.swtbot.swt.finder.SWTBot;
 import org.eclipse.zest.core.widgets.Graph;
 import org.eclipse.zest.core.widgets.GraphItem;
 import org.eclipse.zest.core.widgets.GraphNode;
@@ -28,10 +28,11 @@
 /**
  * Utility class to simulate user events (clicks, etc.) on a {@link Graph}.
  */
-public class GraphicalRobot {
+public class GraphicalRobot extends SWTBot {
 	private final Graph graph;
 
 	public GraphicalRobot(Graph graph) {
+		super(graph.getShell());
 		this.graph = graph;
 	}
 
@@ -108,31 +109,9 @@ public void mouseDown(int x, int y) {
 	 * @param node The graph node to select.
 	 */
 	public void select(GraphNode node) {
-		graph.setSelection(new GraphItem[] { node });
-		select(graph);
-	}
-
-	/**
-	 * This method simulates a {@link SWT#Selection} event using the given
-	 * {@code widget}. Events are sent to the argument.
-	 *
-	 * @param widget The widget to select.
-	 */
-	@SuppressWarnings("static-method")
-	public void select(Widget widget) {
 		Event event = createMouseEvent(SWT.Selection, 1, 1);
-		widget.notifyListeners(event.type, event);
-	}
-
-	/**
-	 * This method simulates a {@link SWT#FocusOut} event using the given
-	 * {@code widget}. Events are sent to the argument.
-	 *
-	 * @param widget The widget whose focus has been lost.
-	 */
-	@SuppressWarnings("static-method")
-	public void focusOut(Widget widget) {
-		widget.notifyListeners(SWT.FocusOut, new Event());
+		graph.setSelection(new GraphItem[] { node });
+		graph.notifyListeners(event.type, event);
 	}
 
 	/**