Streamline AfterClass invocation

Closes #2726

CHANGES.txt

@@ -1,5 +1,6 @@
 Current
 7.6.0
+Fixed: GITHUB-2726: @AfterClass config method is executed for EACH @Test method when parallel == methods (Krishnan Mahadevan)
 Fixed: GITHUB-2752: TestListener is being lost when implenting both IClassListener and ITestListener (Krishnan Mahadevan)
 New:   GITHUB-2724: DataProvider: possibility to unload dataprovider class, when done with it (Dzmitry Sankouski)
 Fixed: GITHUB-217: Configure TestNG to fail when there's a failure in data provider (Krishnan Mahadevan)

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

@@ -51,7 +51,8 @@ public ClassMethodMap(List<ITestNGMethod> methods, XmlMethodSelector xmlMethodSe
   public boolean removeAndCheckIfLast(ITestNGMethod m, Object instance) {
     Collection<ITestNGMethod> l = classMap.get(instance);
     if (l == null) {
-      throw new AssertionError("l should not be null");
+      throw new IllegalStateException(
+          "Could not find any methods associated with test class instance " + instance);
     }
     l.remove(m);
     // It's the last method of this class if all the methods remaining in the list belong to a

testng-core/src/main/java/org/testng/internal/invokers/TestMethodWorker.java

@@ -127,7 +127,9 @@ && doesTaskHavePreRequistes()
       try {
         invokeTestMethods(testMethod, testMthdInst.getInstance());
       } finally {
-        invokeAfterClassMethods(testMethod.getTestClass(), testMthdInst);
+        synchronized (testMethod.getInstance()) {
+          invokeAfterClassMethods(testMethod.getTestClass(), testMthdInst);
+        }
       }
     }
   }

testng-core/src/test/java/test/configuration/ConfigurationTest.java

@@ -1,9 +1,13 @@
 package test.configuration;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 import java.util.Arrays;
 import org.testng.Assert;
 import org.testng.TestNG;
 import org.testng.annotations.Test;
+import org.testng.xml.XmlSuite;
+import test.configuration.issue2726.TestClassSample;
 import test.configuration.issue2743.SuiteRunnerIssueTestSample;
 import test.configuration.sample.ConfigurationTestSample;
 import test.configuration.sample.ExternalConfigurationClassSample;
@@ -39,4 +43,14 @@ public void testSuiteRunnerWithDefaultConfiguration() {
 
     Assert.assertEquals(testNG.getStatus(), 0);
   }
+
+  @Test(description = "GITHUB-2726")
+  public void testAfterClassCalledOnlyOnceForParallelTestMethods() {
+    TestNG testng = create(TestClassSample.class);
+    testng.setParallel(XmlSuite.ParallelMode.METHODS);
+    testng.setVerbose(2);
+    testng.run();
+    assertThat(TestClassSample.beforeLogs).hasSize(1);
+    assertThat(TestClassSample.afterLogs).hasSize(1);
+  }
 }

testng-core/src/test/java/test/configuration/issue2726/TestClassSample.java

@@ -0,0 +1,29 @@
+package test.configuration.issue2726;
+
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+import org.testng.annotations.AfterClass;
+import org.testng.annotations.BeforeClass;
+import org.testng.annotations.Test;
+
+public class TestClassSample {
+
+  public static final List<String> beforeLogs = new CopyOnWriteArrayList<>();
+  public static final List<String> afterLogs = new CopyOnWriteArrayList<>();
+
+  @BeforeClass
+  public void setup() {
+    beforeLogs.add("BEFORE_" + Thread.currentThread().getName());
+  }
+
+  @AfterClass
+  public void tearDown() {
+    afterLogs.add("AFTER_" + Thread.currentThread().getName());
+  }
+
+  @Test
+  public void testA() {}
+
+  @Test
+  public void testB() {}
+}