I would like to write test cases for a GUI. I want to know how do you simulate a click of JButton, or how do you extract the elements of a JTable.

For the purpose of this, I have built a simple GUI that increase the count by 1 if the button is clicked and the JTextfield is empty, but the count is replaced by the integer in the JTextfield if a number is provided. Of course I would like to use Regex to make sure the text entered into the JTextfield is actually an integer, but let’s assume users won’t mess around and enter a non-integer. In addition, the JLabel updates the current count while the JTable adds a new row.

Here’s the code:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.GroupLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.table.DefaultTableModel;


public class sampleGUI extends JFrame implements ActionListener {
    private Integer previous_count;
    private Integer current_count;
    private JButton Button;
    private JTable table;
    private JTextField text;
    private DefaultTableModel model;
    private JScrollPane scroll;
    private JLabel label;

    public sampleGUI() {
        previous_count = null;
        current_count = 0;
        JFrame frame = new JFrame("Sample");
        JPanel panel = new JPanel();

        GroupLayout layout = new GroupLayout(panel);
        panel.setLayout(layout);

        label = new JLabel("Current Count: " + Integer.toString(current_count));
        text = new JTextField(15);
        Button = new JButton("Change the Count!");
        model = new DefaultTableModel();
        model.addColumn("Previous Count");
        model.addColumn("Current Count");
        table = new JTable(model);
        scroll = new JScrollPane(table);

        layout.setHorizontalGroup(layout
                .createParallelGroup(GroupLayout.Alignment.LEADING)
                .addGroup(
                        layout.createSequentialGroup().addComponent(label)
                                .addComponent(text).addComponent(Button))

                .addComponent(scroll));

        layout.setVerticalGroup(layout
                .createSequentialGroup()
                .addGroup(
                        layout.createParallelGroup(
                                GroupLayout.Alignment.BASELINE)
                                .addComponent(label).addComponent(text)
                                .addComponent(Button)).addComponent(scroll));
        Button.addActionListener(this);

        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == Button) {
            if (text.getText().equals("")) {
                previous_count = current_count;
                current_count++;
                label.setText("Current Count: "
                        + Integer.toString(current_count));
                model.addRow(new Object[] { current_count, previous_count });
            } else {
                previous_count = current_count;
                current_count = Integer.parseInt(text.getText());
                label.setText("Current Count: "
                        + Integer.toString(current_count));
                text.setText("");
                model.addRow(new Object[] { current_count, previous_count });
            }
            table.changeSelection(table.getRowCount() - 1, 0, false,
                    false);
        }
    }

    public static void main(final String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                sampleGUI gui = new sampleGUI();
            }
        });
    }
}

Let’s say I would like to simulate opening the GUI, then click the button once without entering any text, then enter 1234 and click the button, then click the button without entering any text, the JTable should have 3 columns: {{1,0}, {1234, 1}, {1235, 1234}}. How can I write the test for that? Thanks!