title: I can not test the Swing GUI with AssertJ
body: <p>I can not test the GUI in my application using the AssertJ library. So as not to spread all the code of your program, wrote a test program to show the essence of the problem.</p>
  
  <pre><code>package AssertJ;
  
  import javax.swing.*;
  import java.awt.*;
  import java.awt.event.ActionEvent;
  import java.awt.event.ActionListener;
  
  public class SomeFrame extends JFrame {
      JFrame frame;
      JLabel label1;
      JButton button1;
  
      public SomeFrame() {
          createGUI();
  
      }
  
      public void createGUI() {
          frame = new JFrame("EspiaServer");
          frame.setLayout(new FlowLayout());
          frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
          frame.setLocationRelativeTo(null);
          frame.setVisible(true);
          label1 = new JLabel("Random");
          button1 = new JButton("Click Me!");
          button1.setName("button");
          button1.setSize(200, 200);
          button1.addActionListener(listener);
          frame.add(label1);
          frame.add(button1);
          frame.pack();
  
  
      }
  
      public static void main(String[] args) {
          new SomeFrame();
      }
  
  
      ActionListener listener = new ActionListener() {
          @Override
          public void actionPerformed(ActionEvent e) {
              int i = (int) (Math.random() * 99999) + 0;
              label1.setText(String.valueOf(i));
          }
      };
  }
  </code></pre>
  
  <p>Here's the test for it:</p>
  
  <pre><code>package AssertJ;
  
  import org.assertj.swing.edt.GuiActionRunner;
  import org.assertj.swing.fixture.FrameFixture;
  import org.junit.Before;
  import org.junit.Test;
  
  
  public class SomeFrameTest {
      private FrameFixture window;
  
      @Before
      public void setUp() {
          SomeFrame frame = GuiActionRunner.execute(() -&gt; new SomeFrame());
          window = new FrameFixture(frame);
          window.show(); // shows the frame to test
      }
  
  
      @Test
      public void createGUI() {
          window.button("button").click();
      }
  }
  </code></pre>
  
  <p>So that's it. The essence of the application. In the frame, there is one button, when pressed, Jlabel changes its value to a random number. The application starts, everything is fine. But when I run the test. He creates the gui of this application and another window in the upper left corner that constantly flashes and twitches. Accordingly, the command <code>window.button ("button").click(); is not satisfied.</code>
  <a href="https://i.stack.imgur.com/h4WgS.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/h4WgS.jpg" alt="enter image description here"></a></p>
  
  <p>After a few seconds, the app throws the exception :</p>
  
  <pre><code>rg.assertj.swing.exception.ComponentLookupException: Unable to find component using matcher org.assertj.swing.core.NameMatcher[name='button', type=javax.swing.JButton, requireShowing=true].
  
  Component hierarchy:
  AssertJ.SomeFrame[name='frame0', title='', enabled=true, visible=true, showing=true]
    javax.swing.JRootPane[]
      javax.swing.JPanel[name='null.glassPane']
      javax.swing.JLayeredPane[]
        javax.swing.JPanel[name='null.contentPane']
  
  
      at org.assertj.swing.core.BasicComponentFinder.componentNotFound(BasicComponentFinder.java:287)
      at org.assertj.swing.core.BasicComponentFinder.find(BasicComponentFinder.java:272)
      at org.assertj.swing.core.BasicComponentFinder.find(BasicComponentFinder.java:265)
      at org.assertj.swing.core.BasicComponentFinder.findByName(BasicComponentFinder.java:200)
      at org.assertj.swing.fixture.AbstractContainerFixture.findByName(AbstractContainerFixture.java:641)
      at org.assertj.swing.fixture.AbstractContainerFixture.button(AbstractContainerFixture.java:143)
      at AssertJ.SomeFrameTest.createGUI(SomeFrameTest.java:23)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
      at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
      at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
      at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
      at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
      at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
      at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
      at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
  </code></pre>