Tutorial 1: Unit Testing A Single GUI Component

• Points in one of four directions
• Fires an event when pressed once
• Fires continuous events when held down

package example;

import junit.extensions.abbot.*;
import abbot.tester.*;

// ComponentTestFixture automatically handles disposal of GUI components,
// among (many) other things.  Always use it when testing GUI components.
public class ArrowButtonTest extends ComponentTestFixture {

    public ArrowButtonTest(String name) { super(name); }

    public static void main(String[] args) {
        TestHelper.runTests(args, ArrowButtonTest.class);
    }
}

We'll need to put the component into a frame for most tests, but there's already a "showFrame" method in the ComponentTestFixture that we inherit. That method puts a nice fat border around our component to make it visible, although that's not strictly necessary. We'll need a ComponentTester to play actions on our component, so add that to the setup:

    private ComponentTester tester;
    protected void setUp() {
        tester = new ComponentTester();
    }
    protected void tearDown() {
        // Default JUnit test runner keeps references to Tests for its
        // lifetime, so TestCase fields won't be GC'd for the lifetime of the
        // runner. 
        tester = null;
    }

Now write the first test, which ensures that an action is fired when the button is clicked.

import java.awt.event.*;
import javax.swing.*;
    ...

    private String clickType;
    public void testClick() {
        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                clickType = ev.getActionCommand();                            
            }
        };

        ArrowButton left = new ArrowButton(ArrowButton.LEFT);
        ArrowButton right = new ArrowButton(ArrowButton.RIGHT);
        ArrowButton up = new ArrowButton(ArrowButton.UP);
        ArrowButton down = new ArrowButton(ArrowButton.DOWN);

        left.addActionListener(al);
        right.addActionListener(al);
        up.addActionListener(al);
        down.addActionListener(al);

        JPanel pane = new JPanel();
        pane.add(left);
        pane.add(right);
        pane.add(up);
        pane.add(down);
        // ComponentTestFixture provides the frame
        showFrame(pane);

        clickType = null;
        tester.actionClick(left);        
        assertEquals("Action failed (left)", ArrowButton.LEFT, clickType);
        clickType = null;
        tester.actionClick(right);        
        assertEquals("Action failed (right)", ArrowButton.RIGHT, clickType);
        clickType = null;
        tester.actionClick(up);        
        assertEquals("Action failed (up)", ArrowButton.UP, clickType);
        clickType = null;
        tester.actionClick(down);        
        assertEquals("Action failed (down)", ArrowButton.DOWN, clickType);
    }

• A set of constants for the arrow direction.
• An addActionListener method (and probably a remove as well).
• A constructor that takes the direction as its only argument.

java -Dabbot.robot.auto_delay=200 -cp classes example.ArrowButtonTest

That leaves only the last bullet to test, repeated events when held down.

    private int count = 0;
    public void testRepeatedFire() {
        ArrowButton arrow = new ArrowButton(ArrowButton.LEFT);
        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                ++count;
            }
        };
        arrow.addActionListener(al);
        showFrame(arrow);

        Dimension size = arrow.getSize();
        // Hold the button down for 5 seconds
        tester.mousePress(arrow);
        tester.actionDelay(5000);
        tester.mouseRelease();
        assertTrue("Didn't get any repeated events", count > 1);
    }

See the full source code for the component example.ArrowButton, and its TestCase, example.ArrowButtonTest.

This project helped in a big way by