#2734 keep the initial order of listeners

CHANGES.txt

@@ -5,6 +5,7 @@ Fixed: assertEqualsNoOrder for Collection and Iterators size check was missing (
 Fixed: GITHUB-2709: Testnames not working together with suites in suite (Martin Aldrin)
 Fixed: GITHUB-2704: IHookable and IConfigurable callback discrepancy (Krishnan Mahadevan)
 Fixed: GITHUB-2637: Upgrade to JDK11 as the minimum JDK requirements (Krishnan Mahadevan)
+Fixed: GITHUB-2734: Keep the initial order of listeners (Andrei Solntsev)
 
 7.5
 Fixed: GITHUB-2701: Bump gradle version to 7.3.3 to support java17 build (ZhangJian He)

testng-core/src/main/java/org/testng/TestRunner.java

@@ -345,7 +345,7 @@ private void initListeners() {
     // Find all the listener factories and collect all the listeners requested in a
     // @Listeners annotation.
     //
-    Set<Class<? extends ITestNGListener>> listenerClasses = Sets.newHashSet();
+    Set<Class<? extends ITestNGListener>> listenerClasses = Sets.newLinkedHashSet();
     Class<? extends ITestNGListenerFactory> listenerFactoryClass = null;
 
     for (IClass cls : getTestClasses()) {

testng-core/src/test/java/org/testng/TestRunnerTest.java

@@ -0,0 +1,94 @@
+package org.testng;
+
+import static java.util.Collections.emptyList;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Listeners;
+import org.testng.annotations.Test;
+import org.testng.internal.Configuration;
+import org.testng.internal.IConfiguration;
+import org.testng.internal.objects.DefaultTestObjectFactory;
+import org.testng.xml.XmlClass;
+import org.testng.xml.XmlSuite;
+import org.testng.xml.XmlTest;
+
+public class TestRunnerTest {
+  @Test
+  public void listenersShouldBeAppliedInDeclarationOrder_one() {
+    TestRunner testRunner = createTestRunner(TestWithOneListener.class);
+
+    List<IConfigurationListener> configurationListeners = testRunner.getConfigurationListeners();
+
+    assertThat(classesOf(configurationListeners, 1)).containsExactly(FooListener.class);
+  }
+
+  @Test
+  public void listenersShouldBeAppliedInDeclarationOrder_two() {
+    TestRunner testRunner = createTestRunner(TestWithTwoListeners.class);
+
+    List<IConfigurationListener> configurationListeners = testRunner.getConfigurationListeners();
+
+    assertThat(classesOf(configurationListeners, 2))
+        .containsExactly(FooListener.class, BarListener.class);
+  }
+
+  @Test
+  public void listenersShouldBeAppliedInDeclarationOrder_three() {
+    TestRunner testRunner = createTestRunner(TestWithThreeListeners.class);
+
+    List<IConfigurationListener> configurationListeners = testRunner.getConfigurationListeners();
+
+    assertThat(classesOf(configurationListeners, 3))
+        .containsExactly(FooListener.class, BarListener.class, ZooListener.class);
+  }
+
+  @Listeners(FooListener.class)
+  public static class TestWithOneListener {
+    @Test
+    public void some() {}
+  }
+
+  @Listeners({FooListener.class, BarListener.class})
+  public static class TestWithTwoListeners {
+    @BeforeMethod
+    public void setup() {}
+
+    @Test
+    public void some() {}
+  }
+
+  @Listeners({FooListener.class, BarListener.class, ZooListener.class})
+  public static class TestWithThreeListeners {
+    @Test
+    public void some() {}
+  }
+
+  public static class FooListener implements IConfigurationListener {}
+
+  public static class BarListener implements IConfigurationListener {}
+
+  public static class ZooListener implements IConfigurationListener {}
+
+  private <T> List<Class<?>> classesOf(List<T> values, int limit) {
+    return values.stream().limit(limit).map(Object::getClass).collect(Collectors.toList());
+  }
+
+  private TestRunner createTestRunner(Class<?> testClass) {
+    IConfiguration configuration = new Configuration();
+    configuration.setObjectFactory(new DefaultTestObjectFactory());
+    XmlSuite xmlSuite = new XmlSuite();
+    XmlTest xmlTest = new XmlTest(xmlSuite);
+    xmlSuite.addTest(xmlTest);
+    XmlClass xmlClass = new XmlClass(testClass.getName());
+    xmlTest.getXmlClasses().add(xmlClass);
+    String outputDir = "build/reports/tests/test";
+    ITestRunnerFactory factory =
+        (suite, test, listeners, classListeners) ->
+            new TestRunner(configuration, suite, test, false, listeners, classListeners);
+    ISuite suite = new SuiteRunner(configuration, xmlSuite, outputDir, factory, (o1, o2) -> 0);
+    return factory.newTestRunner(suite, xmlTest, emptyList(), emptyList());
+  }
+}

testng-core/src/test/resources/testng.xml

@@ -927,6 +927,12 @@
     </classes>
   </test>
 
+  <test name="TestRunner_unit_tests">
+    <classes>
+      <class name="org.testng.TestRunnerTest"/>
+    </classes>
+  </test>
+
   <!--This test depends on System properties. So its intentionally being run at the end
   because the toggling of the system property will affect other tests -->
   <test name = "RunAtLast">