Move constants to a new Constants class and mark as EXPERIMENTAL

Issue: #2229

Author: YongGoose

junit-vintage-engine/src/main/java/org/junit/vintage/engine/Constants.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2015-2025 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junit.vintage.engine;
+
+import static org.apiguardian.api.API.Status.EXPERIMENTAL;
+import static org.apiguardian.api.API.Status.STABLE;
+
+import org.apiguardian.api.API;
+
+/**
+ * Collection of constants related to the {@link VintageTestEngine}.
+ *
+ * @since 5.12
+ */
+@API(status = STABLE, since = "5.12")
+public final class Constants {
+
+	/**
+	 * Indicates whether parallel execution is enabled for the JUnit Vintage engine.
+	 *
+	 * <p>Set this property to {@code true} to enable parallel execution of tests.
+	 * Defaults to {@code false}.
+	 *
+	 * @since 5.12
+	 */
+	@API(status = EXPERIMENTAL, since = "5.12")
+	public static final String PARALLEL_EXECUTION_ENABLED = "junit.vintage.execution.parallel.enabled";
+
+	/**
+	 * Specifies the size of the thread pool to be used for parallel execution.
+	 *
+	 * <p>Set this property to an integer value to specify the number of threads
+	 * to be used for parallel execution. Defaults to the number of available
+	 * processors.
+	 *
+	 * @since 5.12
+	 */
+	@API(status = EXPERIMENTAL, since = "5.12")
+	public static final String PARALLEL_POOL_SIZE = "junit.vintage.execution.parallel.pool-size";
+
+	private Constants() {
+		/* no-op */
+	}
+
+}

junit-vintage-engine/src/main/java/org/junit/vintage/engine/VintageTestEngine.java

@@ -12,6 +12,8 @@
 
 import static org.apiguardian.api.API.Status.INTERNAL;
 import static org.junit.platform.engine.TestExecutionResult.successful;
+import static org.junit.vintage.engine.Constants.PARALLEL_EXECUTION_ENABLED;
+import static org.junit.vintage.engine.Constants.PARALLEL_POOL_SIZE;
 import static org.junit.vintage.engine.descriptor.VintageTestDescriptor.ENGINE_ID;
 
 import java.util.ArrayList;
@@ -52,29 +54,6 @@ public final class VintageTestEngine implements TestEngine {
 	private static final int DEFAULT_THREAD_POOL_SIZE = Runtime.getRuntime().availableProcessors();
 	private static final int SHUTDOWN_TIMEOUT_SECONDS = 30;
 
-	/**
-	 * Indicates whether parallel execution is enabled for the JUnit Vintage engine.
-	 *
-	 * <p>Set this property to {@code true} to enable parallel execution of tests.
-	 * Defaults to {@code false}.
-	 *
-	 * @since 5.12
-	 */
-	@API(status = INTERNAL, since = "5.12")
-	public static final String PARALLEL_EXECUTION_ENABLED = "junit.vintage.execution.parallel.enabled";
-
-	/**
-	 * Specifies the size of the thread pool to be used for parallel execution.
-	 *
-	 * <p>Set this property to an integer value to specify the number of threads
-	 * to be used for parallel execution. Defaults to the number of available
-	 * processors.
-	 *
-	 * @since 5.12
-	 */
-	@API(status = INTERNAL, since = "5.12")
-	public static final String PARALLEL_POOL_SIZE = "junit.vintage.execution.parallel.pool-size";
-
 	@Override
 	public String getId() {
 		return ENGINE_ID;

junit-vintage-engine/src/test/java/org/junit/vintage/engine/execution/ParallelExecutionIntegrationTests.java

@@ -15,6 +15,8 @@
 import static org.junit.platform.testkit.engine.EventConditions.event;
 import static org.junit.platform.testkit.engine.EventConditions.finishedSuccessfully;
 import static org.junit.platform.testkit.engine.EventConditions.started;
+import static org.junit.vintage.engine.Constants.PARALLEL_EXECUTION_ENABLED;
+import static org.junit.vintage.engine.Constants.PARALLEL_POOL_SIZE;
 import static org.junit.vintage.engine.descriptor.VintageTestDescriptor.SEGMENT_TYPE_RUNNER;
 import static org.junit.vintage.engine.samples.junit4.JUnit4ParallelTestCase.AbstractBlockingTestCase;
 import static org.junit.vintage.engine.samples.junit4.JUnit4ParallelTestCase.FirstTestCase;
@@ -42,9 +44,6 @@
 
 class ParallelExecutionIntegrationTests {
 
-	private static final String PARALLEL_EXECUTION_ENABLED = "junit.vintage.execution.parallel.enabled";
-	private static final String PARALLEL_POOL_SIZE = "junit.vintage.execution.parallel.pool-size";
-
 	@Test
 	void executesTestClassesInParallel(TestReporter reporter) {
 		AbstractBlockingTestCase.threadNames.clear();