Unstable test 'test_CREATE_inside'

See https://github.com/eclipse-windowbuilder/windowbuilder/pull/1347/checks?check_run_id=60402436562

expected: <package test;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class Test extends JPanel {
 public Test() {
  setLayout(new GridLayout());
  {
   JPanel panel_1 = new JPanel();
   add(panel_1);
   {
    JButton button = new JButton();
    panel_1.add(button);
   }
  }
 }
}
> but was: <package test;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class Test extends JPanel {
 public Test() {
  setLayout(new GridLayout());
  {
   JPanel panel_1 = new JPanel();
   add(panel_1);
  }
 }
}
>
org.opentest4j.AssertionFailedError: 
expected: <package test;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class Test extends JPanel {
	public Test() {
		setLayout(new GridLayout());
		{
			JPanel panel_1 = new JPanel();
			add(panel_1);
			{
				JButton button = new JButton();
				panel_1.add(button);
			}
		}
	}
}
> but was: <package test;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class Test extends JPanel {
	public Test() {
		setLayout(new GridLayout());
		{
			JPanel panel_1 = new JPanel();
			add(panel_1);
		}
	}
}
>
	at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
	at org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
	at org.junit.jupiter.api.AssertEquals.failNotEqual(AssertEquals.java:197)
	at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:182)
	at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:177)
	at org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:1145)
	at org.eclipse.wb.tests.designer.core.AbstractJavaTest.assertEditor(AbstractJavaTest.java:273)
	at org.eclipse.wb.tests.designer.swing.SwingGefTest.assertEditor(SwingGefTest.java:115)
	at org.eclipse.wb.tests.designer.editor.validator.BorderOfChildLayoutRequestValidatorTest.test_CREATE_inside(BorderOfChildLayoutRequestValidatorTest.java:59)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at org.eclipse.wb.tests.designer.core.model.parser.AbstractJavaInfoTest$JavaInfoExtension.interceptTestMethod(AbstractJavaInfoTest.java:85)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
Jan. 14, 2026 8:44:41 PM org.eclipse.wb.tests.designer.tests.DesignerTestCase$LoggerExtension beforeTestExecution

pull request のチェックで発生した失敗から参照されている BorderOfChildLayoutRequestValidatorTest.test_CREATE_inside から始め、テストを再現して、生成されたエディター出力で JButton が省略される理由を特定します。期待される Java ソースと実際の Java ソースを比較し、根本にある不安定性に対処した後、テストが一貫してパスすることを確認します。