Fix bug in WebClientDataBufferAllocatingTests

Prior to this commit, the parameterized DataBufferFactory was never
actually used when setting up the WebClient for each test. This was due
to an oversight when migrating from JUnit 4 to JUnit Jupiter.

See: https://github.com/reactor/reactor-netty/issues/860

This commit fixes this by converting the existing @BeforeEach method to
a local setup method that is invoked from each
@ParameterizedDataBufferAllocatingTest method.

In addition, in order to avoid the 2 second "quiet period" that is
incurred when destroying the ReactorResourceFactory, this commit moves
the setup and destruction of the ReactorResourceFactory to new
@BeforeAll and @AfterAll methods.

The test instance lifecycle has also been switched to PER_CLASS to avoid
static state in the test class.

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientDataBufferAllocatingTests.java

@@ -25,8 +25,10 @@ import io.netty.buffer.ByteBufAllocator;
 import io.netty.channel.ChannelOption;
 import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
+import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.TestInstance;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
@@ -42,6 +44,7 @@ import org.springframework.http.client.reactive.ReactorResourceFactory;
 import org.springframework.web.reactive.function.UnsupportedMediaTypeException;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.TestInstance.Lifecycle.PER_CLASS;
 
 /**
  * WebClient integration tests focusing on data buffer management.
@@ -49,23 +52,29 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Rossen Stoyanchev
  * @author Sam Brannen
  */
-public class WebClientDataBufferAllocatingTests extends AbstractDataBufferAllocatingTests {
+@TestInstance(PER_CLASS)
+class WebClientDataBufferAllocatingTests extends AbstractDataBufferAllocatingTests {
 
 	private static final Duration DELAY = Duration.ofSeconds(5);
 
-
 	private final ReactorResourceFactory factory = new ReactorResourceFactory();
-
-	private final MockWebServer server = new MockWebServer();
-
+	private MockWebServer server;
 	private WebClient webClient;
 
 
-	@BeforeEach
-	public void setUp() {
-		this.factory.setUseGlobalResources(false);
-		this.factory.afterPropertiesSet();
+	@BeforeAll
+	void setUpReactorResourceFactory() {
+		factory.afterPropertiesSet();
+	}
 
+	@AfterAll
+	void destroyReactorResourceFactory() {
+		factory.destroy();
+	}
+
+	private void setUp(DataBufferFactory bufferFactory) {
+		super.bufferFactory = bufferFactory;
+		this.server = new MockWebServer();
 		this.webClient = WebClient
 				.builder()
 				.clientConnector(initConnector())
@@ -74,9 +83,11 @@ public class WebClientDataBufferAllocatingTests extends AbstractDataBufferAlloca
 	}
 
 	private ReactorClientHttpConnector initConnector() {
-		if (bufferFactory instanceof NettyDataBufferFactory) {
-			ByteBufAllocator allocator = ((NettyDataBufferFactory) bufferFactory).getByteBufAllocator();
-			return new ReactorClientHttpConnector(this.factory, httpClient ->
+		assertThat(super.bufferFactory).isNotNull();
+
+		if (super.bufferFactory instanceof NettyDataBufferFactory) {
+			ByteBufAllocator allocator = ((NettyDataBufferFactory) super.bufferFactory).getByteBufAllocator();
+			return new ReactorClientHttpConnector(factory, httpClient ->
 					httpClient.tcpConfiguration(tcpClient -> tcpClient.option(ChannelOption.ALLOCATOR, allocator)));
 		}
 		else {
@@ -85,15 +96,14 @@ public class WebClientDataBufferAllocatingTests extends AbstractDataBufferAlloca
 	}
 
 	@AfterEach
-	public void shutDown() throws InterruptedException {
+	void shutDown() throws InterruptedException {
 		waitForDataBufferRelease(Duration.ofSeconds(2));
-		this.factory.destroy();
 	}
 
 
 	@ParameterizedDataBufferAllocatingTest
-	public void bodyToMonoVoid(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void bodyToMonoVoid(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		this.server.enqueue(new MockResponse()
 				.setResponseCode(201)
@@ -110,8 +120,8 @@ public class WebClientDataBufferAllocatingTests extends AbstractDataBufferAlloca
 	}
 
 	@ParameterizedDataBufferAllocatingTest // SPR-17482
-	public void bodyToMonoVoidWithoutContentType(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void bodyToMonoVoidWithoutContentType(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		this.server.enqueue(new MockResponse()
 				.setResponseCode(HttpStatus.ACCEPTED.value())
@@ -127,40 +137,40 @@ public class WebClientDataBufferAllocatingTests extends AbstractDataBufferAlloca
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void onStatusWithBodyNotConsumed(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void onStatusWithBodyNotConsumed(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		RuntimeException ex = new RuntimeException("response error");
 		testOnStatus(ex, response -> Mono.just(ex));
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void onStatusWithBodyConsumed(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void onStatusWithBodyConsumed(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		RuntimeException ex = new RuntimeException("response error");
 		testOnStatus(ex, response -> response.bodyToMono(Void.class).thenReturn(ex));
 	}
 
 	@ParameterizedDataBufferAllocatingTest // SPR-17473
-	public void onStatusWithMonoErrorAndBodyNotConsumed(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void onStatusWithMonoErrorAndBodyNotConsumed(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		RuntimeException ex = new RuntimeException("response error");
 		testOnStatus(ex, response -> Mono.error(ex));
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void onStatusWithMonoErrorAndBodyConsumed(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void onStatusWithMonoErrorAndBodyConsumed(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		RuntimeException ex = new RuntimeException("response error");
 		testOnStatus(ex, response -> response.bodyToMono(Void.class).then(Mono.error(ex)));
 	}
 
 	@ParameterizedDataBufferAllocatingTest // gh-23230
-	public void onStatusWithImmediateErrorAndBodyNotConsumed(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void onStatusWithImmediateErrorAndBodyNotConsumed(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		RuntimeException ex = new RuntimeException("response error");
 		testOnStatus(ex, response -> {
@@ -169,8 +179,8 @@ public class WebClientDataBufferAllocatingTests extends AbstractDataBufferAlloca
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void releaseBody(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void releaseBody(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		this.server.enqueue(new MockResponse()
 				.setResponseCode(200)
@@ -188,8 +198,8 @@ public class WebClientDataBufferAllocatingTests extends AbstractDataBufferAlloca
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void exchangeToBodilessEntity(String displayName, DataBufferFactory bufferFactory) {
-		super.bufferFactory = bufferFactory;
+	void exchangeToBodilessEntity(String displayName, DataBufferFactory bufferFactory) {
+		setUp(bufferFactory);
 
 		this.server.enqueue(new MockResponse()
 				.setResponseCode(201)