Re-enable BlockHound integration tests

Prior to this commit, our BlockHound integration tests were disabled
after the migration to a JDK 17 baseline since the build now always
runs on JDK 14 or higher.

To re-enable the tests we now supply the deprecated
-XX:+AllowRedefinitionToAddDeleteMethods command-line argument to the JVM
for tests in the Gradle build. Users can also configure this manually
within an IDE to run SpringCoreBlockHoundIntegrationTests.

If that command-line argument is removed from the JVM at some point in
the future, we will need to investigate an alternative solution.

See reactor/BlockHound#33 for details.

spring-core/spring-core.gradle

@@ -92,4 +92,10 @@ test {
 	// Make sure the classes dir is used on the test classpath (required by ResourceTests).
 	// When test fixtures are involved, the JAR is used by default.
 	classpath = sourceSets.main.output.classesDirs + classpath - files(jar.archiveFile)
+
+	// Ensure that BlockHound tests run on JDK 13+. For details, see:
+	// https://github.com/reactor/BlockHound/issues/33
+	jvmArgs += [
+		"-XX:+AllowRedefinitionToAddDeleteMethods"
+	]
 }

spring-core/src/test/java/org/springframework/core/SpringCoreBlockHoundIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,7 +22,6 @@
 
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.condition.DisabledForJreRange;
 import reactor.blockhound.BlockHound;
 import reactor.core.scheduler.ReactorBlockHoundIntegration;
 import reactor.core.scheduler.Schedulers;
@@ -32,16 +31,23 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
-import static org.junit.jupiter.api.condition.JRE.JAVA_14;
 
 /**
  * Tests to verify the spring-core BlockHound integration rules.
  *
+ * <p>NOTE: to run this test class in the IDE, you need to specify the following
+ * JVM argument. For details, see
+ * <a href="https://github.com/reactor/BlockHound/issues/33">BlockHound issue 33</a>.
+ *
+ * <pre style="code">
+ * -XX:+AllowRedefinitionToAddDeleteMethods
+ * </pre>
+ *
  * @author Rossen Stoyanchev
+ * @author Sam Brannen
  * @since 5.2.4
  */
-@DisabledForJreRange(min = JAVA_14)
-public class SpringCoreBlockHoundIntegrationTests {
+class SpringCoreBlockHoundIntegrationTests {
 
 
 	@BeforeAll
@@ -64,7 +70,7 @@ void localVariableTableParameterNameDiscoverer() {
 		testNonBlockingTask(() -> {
 			Method setName = TestObject.class.getMethod("setName", String.class);
 			String[] names = new LocalVariableTableParameterNameDiscoverer().getParameterNames(setName);
-			assertThat(names).isEqualTo(new String[] {"name"});
+			assertThat(names).containsExactly("name");
 		});
 	}