Add TestTask::getTestDescriptor method (#4717)

Since a `TestTask` always corresponds to a specific test node, making 
its descriptor available for further analysis in custom test engines may
be useful.

Resolves #4711.

---------

Co-authored-by: Marc Philipp <mail@marcphilipp.de>

Author: eric6iese

junit-platform-engine/src/main/java/org/junit/platform/engine/support/hierarchical/HierarchicalTestExecutorService.java

@@ -10,6 +10,7 @@
 
 package org.junit.platform.engine.support.hierarchical;
 
+import static org.apiguardian.api.API.Status.EXPERIMENTAL;
 import static org.apiguardian.api.API.Status.STABLE;
 
 import java.util.List;
@@ -18,6 +19,7 @@
 import org.apiguardian.api.API;
 import org.jspecify.annotations.Nullable;
 import org.junit.platform.engine.ExecutionRequest;
+import org.junit.platform.engine.TestDescriptor;
 import org.junit.platform.engine.support.hierarchical.Node.ExecutionMode;
 
 /**
@@ -95,6 +97,17 @@ interface TestTask {
 		 */
 		ResourceLock getResourceLock();
 
+		/**
+		 * Get the {@linkplain TestDescriptor test descriptor} of this task.
+		 *
+		 * @throws UnsupportedOperationException if not supported for this TestTask implementation
+		 * @since 6.0
+		 */
+		@API(status = EXPERIMENTAL, since = "6.0")
+		default TestDescriptor getTestDescriptor() {
+			throw new UnsupportedOperationException();
+		}
+
 		/**
 		 * Execute this task.
 		 */

junit-platform-engine/src/main/java/org/junit/platform/engine/support/hierarchical/NodeTestTask.java

@@ -86,6 +86,11 @@ public ExecutionMode getExecutionMode() {
 				.orElseGet(node::getExecutionMode);
 	}
 
+	@Override
+	public TestDescriptor getTestDescriptor() {
+		return testDescriptor;
+	}
+
 	@Override
 	public String toString() {
 		return "NodeTestTask [" + testDescriptor + "]";