Add start and stop for RSocket client and tester

Closes gh-378

spring-graphql-test/src/main/java/org/springframework/graphql/test/tester/DefaultRSocketGraphQlTesterBuilder.java

@@ -21,6 +21,7 @@ import java.util.List;
 import java.util.function.Consumer;
 
 import io.rsocket.transport.ClientTransport;
+import reactor.core.publisher.Mono;
 
 import org.springframework.core.codec.Decoder;
 import org.springframework.core.codec.Encoder;
@@ -141,6 +142,16 @@ public class DefaultRSocketGraphQlTesterBuilder
 			this.builderInitializer = builderInitializer;
 		}
 
+		@Override
+		public Mono<Void> start() {
+			return this.rsocketGraphQlClient.start();
+		}
+
+		@Override
+		public Mono<Void> stop() {
+			return this.rsocketGraphQlClient.stop();
+		}
+
 		@Override
 		public RSocketGraphQlTester.Builder<?> mutate() {
 			DefaultRSocketGraphQlTesterBuilder builder = new DefaultRSocketGraphQlTesterBuilder(this.rsocketGraphQlClient);

spring-graphql-test/src/main/java/org/springframework/graphql/test/tester/RSocketGraphQlTester.java

@@ -21,7 +21,9 @@ import java.net.URI;
 import java.util.function.Consumer;
 
 import io.rsocket.transport.ClientTransport;
+import reactor.core.publisher.Mono;
 
+import org.springframework.graphql.client.RSocketGraphQlClient;
 import org.springframework.messaging.rsocket.RSocketRequester;
 import org.springframework.util.MimeType;
 
@@ -33,6 +35,19 @@ import org.springframework.util.MimeType;
  */
 public interface RSocketGraphQlTester extends GraphQlTester {
 
+	/**
+	 * Start the RSocket session.
+	 * @return {@code Mono} that completes when the underlying session is started
+	 */
+	Mono<Void> start();
+
+	/**
+	 * Stop the RSocket session.
+	 * @return {@code Mono} that completes when the underlying session is closed
+	 * <p>Note that currently this method not differed and does not wait,
+	 * see {@link RSocketGraphQlClient#stop()}
+	 */
+	Mono<Void> stop();
 
 	@Override
 	RSocketGraphQlTester.Builder<?> mutate();