Several tests in "org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text" are flapping #106

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1. niraj-modi

   added

   junitJUnit test failureJUnit test failure

   on May 9, 2022
2. SyntevoAlex commented on Jul 4, 2023

   

   SyntevoAlex

   on Jul 4, 2023

   Last edited by SyntevoAlex

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   I have investigated that.

   All clipboard-related tests can fail, I myself seen these:

   Test_org_eclipse_swt_widgets_Text.test_consistency_Segments
   Test_org_eclipse_swt_widgets_Text.test_copy
   Test_org_eclipse_swt_widgets_Text.test_paste
   Test_org_eclipse_swt_widgets_Combo.test_consistency_Segments
   Test_org_eclipse_swt_widgets_Combo.test_copy
   Test_org_eclipse_swt_custom_CCombo.test_cut
   

   The failure is chance based, with around 1% chance.

   It's easy to reproduce by running this code:

   final Display display = new Display();
   final Shell shell = new Shell(display);
   shell.setLayout (new GridLayout (1, true));
   
   Text text = new Text(shell, 0);
   System.out.format("%X = handle%n", text.handle);
   
   shell.pack();
   shell.open();
   while (display.readAndDispatch()) {};
   
   for (int i = 0; i < 10000; i++) {
   	text.setText("01234567890");
   	text.setSelection(2, 5);
   	text.cut();
   	if (!text.getText().equals("01567890")) {
   		System.out.println("Error!");
   	}
   }
   
   while (!shell.isDisposed()) {
   	if (!display.readAndDispatch()) {
   		display.sleep();
   	}
   }
   
   display.dispose();

   I have debugged, the problem is that OpenClipboard() fails inside WINAPI handler for messages like WM_COPY or WM_CUT. Can be seen with WinDBG breakpoint: bp win32u!NtUserOpenClipboard+0x14 ".if (@rax == 1) {g}".

   I'm not exactly sure what causes the failure. It doesn't make sense that some other app repeatedly claims ownership of clipboard, but maybe that is indeed the case. Maybe when SWT copies something to clipboard, some other app checks that, and if SWT tries to copy again while app is checking, it fails. Getting a definitive answer would require kernel debugging, and I don't think the Issue is important enough to spend time on that.
3. basilevs commented on Jan 27, 2024

   

   basilevs

   on Jan 27, 2024

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   https://github.com/eclipse-platform/eclipse.platform.swt/actions/runs/7674714373/job/20919789301

   org.junit.ComparisonFailure: expected:<[00000]> but was:<[]>
   	at org.junit.Assert.assertEquals(Assert.java:117)
   	at org.junit.Assert.assertEquals(Assert.java:146)
   	at org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text.test_copy(Test_org_eclipse_swt_widgets_Text.java:324)
   
4. fedejeanne commented on Jun 18, 2024

   

   fedejeanne

   on Jun 18, 2024

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   Also failed in this run of #1265

   expected:<[00000]> but was:<[]>
   org.junit.ComparisonFailure: expected:<[00000]> but was:<[]>
   	at org.junit.Assert.assertEquals(Assert.java:117)
   	at org.junit.Assert.assertEquals(Assert.java:146)
   	at org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text.test_copy(Test_org_eclipse_swt_widgets_Text.java:343)
   ...
5. fedejeanne

   changed the title [-]test_cut (org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text) is flapping[/-] [+]Several tests in "org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text" are flapping[/+] on Jun 18, 2024
6. deepika-u commented on Jan 9, 2025

   

   deepika-u

   on Jan 9, 2025

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   Can this also be closed?
   As i see the tests pass now

   <testcase classname="org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text" name="test_cut" time="0.015"/>
   <testcase classname="org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text" name="test_consistency_Segments" time="0.073"/>
   <testcase classname="org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text" name="test_copy" time="0.016"/>
   <testcase classname="org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Text" name="test_paste" time="0.022"/>
   <testcase classname="org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Combo" name="test_consistency_Segments" time="0.053"/>
   <testcase classname="org.eclipse.swt.tests.junit.Test_org_eclipse_swt_widgets_Combo" name="test_copy" time="0.006"/>
   <testcase classname="org.eclipse.swt.tests.junit.Test_org_eclipse_swt_custom_CCombo" name="test_cut" time="0.006"/>
   

   From -> https://download.eclipse.org/eclipse/downloads/drops4/I20250108-1800/testresults/xml/org.eclipse.swt.tests_ep435I-unit-win32-x86_64-java21_win32.win32.x86_64_21.xml
7. fedejeanne commented on Jan 13, 2025

   

   fedejeanne

   on Jan 13, 2025

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   The problem seems to be there still:

   

   Or do you know of any fix @deepika-u ?

   To reproduce

   Let the test class run hundreds of times by making it parameterized

   @RunWith(Parameterized.class)
   public class Test_org_eclipse_swt_widgets_Text extends Test_org_eclipse_swt_widgets_Scrollable {
   
   ...
   
   @Parameters
   public static Collection<Integer> params() {
   	return  IntStream.range(1, 301).boxed().collect(Collectors.toList());
   }
   
   public Test_org_eclipse_swt_widgets_Text(Integer i) { }
   ...
   }
8. HeikoKlare

   added 2 commits that reference this issue on Feb 14, 2026

   Improve stability of Text cut/copy/paste tests on Windows

   ...

   592b91b

   Improve stability of Text cut/copy/paste tests on Windows

   ...

   995f2f8
9. HeikoKlare

   added 3 commits that reference this issue on Mar 2, 2026

   Improve stability of Text cut/copy/paste tests on Windows

   ...

   f3abc7b

   Improve stability of Text cut/copy/paste tests on Windows

   ...

   1829c7d

   Improve stability of Text cut/copy/paste tests on Windows

   ...

   696cc30
10. HeikoKlare

    closed this as completedin #3081on Mar 2, 2026