Introduce adding 'shared resources' programmatically

documentation/src/docs/asciidoc/link-attributes.adoc

@@ -128,6 +128,7 @@ endif::[]
 :Execution:                                  {javadoc-root}/org.junit.jupiter.api/org/junit/jupiter/api/parallel/Execution.html[@Execution]
 :Isolated:                                   {javadoc-root}/org.junit.jupiter.api/org/junit/jupiter/api/parallel/Isolated.html[@Isolated]
 :ResourceLock:                               {javadoc-root}/org.junit.jupiter.api/org/junit/jupiter/api/parallel/ResourceLock.html[@ResourceLock]
+:ResourceLocksProvider:                      {javadoc-root}/org.junit.jupiter.api/org/junit/jupiter/api/parallel/ResourceLocksProvider.html[ResourceLocksProvider]
 :Resources:                                  {javadoc-root}/org.junit.jupiter.api/org/junit/jupiter/api/parallel/Resources.html[Resources]
 // Jupiter Extension APIs
 :extension-api-package:                      {javadoc-root}/org.junit.jupiter.api/org/junit/jupiter/api/extension/package-summary.html[org.junit.jupiter.api.extension]

documentation/src/docs/asciidoc/release-notes/release-notes-5.12.0-M1.adoc

@@ -54,6 +54,8 @@ JUnit repository on GitHub.
   `@ConvertWith`), and `ArgumentsAggregator` (declared via `@AggregateWith`)
   implementations can now use constructor injection from registered `ParameterResolver`
   extensions.
+* Introduce adding `shared resources` in runtime via new `@ResourceLocks#provider` attribute
+  which accepts implementations of `ResourceLocksProvider`.
 
 
 [[release-notes-5.12.0-M1-junit-vintage]]

documentation/src/docs/asciidoc/user-guide/writing-tests.adoc

@@ -2943,10 +2943,18 @@ execution. The shared resource is identified by a unique name which is a `String
 name can be user-defined or one of the predefined constants in `{Resources}`:
 `SYSTEM_PROPERTIES`, `SYSTEM_OUT`, `SYSTEM_ERR`, `LOCALE`, or `TIME_ZONE`.
 
-If the tests in the following example were run in parallel _without_ the use of
-{ResourceLock}, they would be _flaky_. Sometimes they would pass, and at other times they
-would fail due to the inherent race condition of writing and then reading the same JVM
-System Property.
+`{ResourceLock}` annotation has 'providers' attribute
+which accepts an array of one or more classes implementing `{ResourceLocksProvider}`
+interface. This interface allows to add shared resources in runtime.
+
+Note that resources declared "statically" with `{ResourceLock}` annotation
+are combined with resources added "dynamically" with `{ResourceLocksProvider}`
+interface.
+
+If the tests in the following examples were run in parallel _without_ the use of
+`{ResourceLock}` or `{ResourceLocksProvider}`, they would be _flaky_.
+Sometimes they would pass, and at other times they would fail due to
+the inherent race condition of writing and then reading the same JVM System Property.
 
 When access to shared resources is declared using the `{ResourceLock}` annotation, the
 JUnit Jupiter engine uses this information to ensure that no conflicting tests are run in
@@ -2970,8 +2978,15 @@ parallel with each other but not while any other test that requires `READ_WRITE`
 to the same shared resource is running.
 
 [source,java]
+.Declaring shared resources "statically" with `{ResourceLock}` annotation
+----
+include::{testDir}/example/sharedresources/StaticSharedResourcesDemo.java[tags=user_guide]
+----
+
+[source,java]
+.Adding shared resources "dynamically" with `{ResourceLocksProvider}` interface
 ----
-include::{testDir}/example/SharedResourcesDemo.java[tags=user_guide]
+include::{testDir}/example/sharedresources/DynamicSharedResourcesDemo.java[tags=user_guide]
 ----
 
 

documentation/src/test/java/example/sharedresources/DynamicSharedResourcesDemo.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2015-2024 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 example.sharedresources;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.parallel.ExecutionMode.CONCURRENT;
+import static org.junit.jupiter.api.parallel.ResourceAccessMode.READ;
+import static org.junit.jupiter.api.parallel.ResourceAccessMode.READ_WRITE;
+import static org.junit.jupiter.api.parallel.Resources.SYSTEM_PROPERTIES;
+
+import java.lang.reflect.Method;
+import java.util.HashSet;
+import java.util.Properties;
+import java.util.Set;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.parallel.Execution;
+import org.junit.jupiter.api.parallel.ResourceAccessMode;
+import org.junit.jupiter.api.parallel.ResourceLock;
+import org.junit.jupiter.api.parallel.ResourceLocksProvider;
+
+// tag::user_guide[]
+@Execution(CONCURRENT)
+@ResourceLock(providers = DynamicSharedResourcesDemo.Provider.class)
+class DynamicSharedResourcesDemo {
+
+	private Properties backup;
+
+	@BeforeEach
+	void backup() {
+		backup = new Properties();
+		backup.putAll(System.getProperties());
+	}
+
+	@AfterEach
+	void restore() {
+		System.setProperties(backup);
+	}
+
+	@Test
+	void customPropertyIsNotSetByDefault() {
+		assertNull(System.getProperty("my.prop"));
+	}
+
+	@Test
+	void canSetCustomPropertyToApple() {
+		System.setProperty("my.prop", "apple");
+		assertEquals("apple", System.getProperty("my.prop"));
+	}
+
+	@Test
+	void canSetCustomPropertyToBanana() {
+		System.setProperty("my.prop", "banana");
+		assertEquals("banana", System.getProperty("my.prop"));
+	}
+
+	static class Provider implements ResourceLocksProvider {
+
+		@Override
+		public Set<Lock> provideForMethod(Class<?> testClass, Method testMethod) {
+			ResourceAccessMode mode;
+			if (testMethod.getName().startsWith("canSet")) {
+				mode = READ_WRITE;
+			}
+			else {
+				mode = READ;
+			}
+			Set<Lock> locks = new HashSet<>();
+			locks.add(new Lock(SYSTEM_PROPERTIES, mode));
+			return locks;
+		}
+	}
+
+}
+// end::user_guide[]

documentation/src/test/java/example/SharedResourcesDemo.java → documentation/src/test/java/example/sharedresources/StaticSharedResourcesDemo.java

@@ -8,7 +8,7 @@
  * https://www.eclipse.org/legal/epl-v20.html
  */
 
-package example;
+package example.sharedresources;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNull;
@@ -27,7 +27,7 @@
 
 // tag::user_guide[]
 @Execution(CONCURRENT)
-class SharedResourcesDemo {
+class StaticSharedResourcesDemo {
 
 	private Properties backup;
 

junit-jupiter-api/src/main/java/org/junit/jupiter/api/parallel/ResourceAccessMode.java

@@ -19,6 +19,7 @@
  *
  * @since 5.3
  * @see ResourceLock
+ * @see ResourceLocksProvider.Lock
  */
 @API(status = STABLE, since = "5.10")
 public enum ResourceAccessMode {

junit-jupiter-api/src/main/java/org/junit/jupiter/api/parallel/ResourceLock.java

@@ -10,6 +10,7 @@
 
 package org.junit.jupiter.api.parallel;
 
+import static org.apiguardian.api.API.Status.EXPERIMENTAL;
 import static org.apiguardian.api.API.Status.STABLE;
 
 import java.lang.annotation.ElementType;
@@ -48,10 +49,20 @@
  * <p>Since JUnit Jupiter 5.4, this annotation is {@linkplain Inherited inherited}
  * within class hierarchies.
  *
+ * <p>Since JUnit Jupiter 5.12, this annotation supports adding shared resources
+ * in runtime via {@link ResourceLock#providers}.
+ *
+ * <p>Resources declared "statically" using {@link #value()} and {@link #mode()}
+ * are combined with "dynamic" resources added via {@link #providers()}.
+ * For example, declaring resource "A" via {@code @ResourceLock("A")}
+ * and resource "B" via a provider returning {@code new Lock("B")} will result
+ * in two shared resources "A" and "B".
+ *
  * @see Isolated
  * @see Resources
  * @see ResourceAccessMode
  * @see ResourceLocks
+ * @see ResourceLocksProvider
  * @since 5.3
  */
 @API(status = STABLE, since = "5.10")
@@ -64,17 +75,32 @@
 	/**
 	 * The resource key.
 	 *
+	 * <p>Defaults to an empty string.
+	 *
 	 * @see Resources
+	 * @see ResourceLocksProvider.Lock#getKey()
 	 */
-	String value();
+	String value() default "";
 
 	/**
 	 * The resource access mode.
 	 *
 	 * <p>Defaults to {@link ResourceAccessMode#READ_WRITE READ_WRITE}.
 	 *
 	 * @see ResourceAccessMode
+	 * @see ResourceLocksProvider.Lock#getAccessMode()
 	 */
 	ResourceAccessMode mode() default ResourceAccessMode.READ_WRITE;
 
+	/**
+	 * An array of one or more classes implementing {@link ResourceLocksProvider}.
+	 *
+	 * <p>Defaults to an empty array.
+	 *
+	 * @see ResourceLocksProvider.Lock
+	 * @since 5.12
+	 */
+	@API(status = EXPERIMENTAL, since = "5.12")
+	Class<? extends ResourceLocksProvider>[] providers() default {};
+
 }