Updates to migration guide

- Relates #742

spring-statemachine-core/src/test/java/org/springframework/statemachine/docs/DocsMigrationTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2019 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.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.statemachine.docs;
+
+import org.springframework.messaging.Message;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.statemachine.StateMachine;
+import org.springframework.statemachine.StateMachineEventResult;
+
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+public class DocsMigrationTests {
+
+	StateMachine<String, String> machine;
+
+	interface StateMachineDocs<S, E> extends StateMachine<S, E> {
+		// tag::snippetA[]
+		Flux<StateMachineEventResult<S, E>> sendEvent(Mono<Message<E>> event);
+
+		Flux<StateMachineEventResult<S, E>> sendEvents(Flux<Message<E>> events);
+		// end::snippetA[]
+	}
+
+	public void sample1() {
+		// tag::snippetB1[]
+		Message<String> message = MessageBuilder.withPayload("EVENT").build();
+		machine.sendEvent(Mono.just(message)).subscribe();
+		// end::snippetB1[]
+		// tag::snippetB2[]
+		machine.sendEvents(Flux.just(message)).subscribe();
+		// end::snippetB2[]
+	}
+
+	public void sample2() {
+		// tag::snippetB3[]
+		Mono<Message<String>> mono = Mono.just(MessageBuilder.withPayload("EVENT").build());
+		machine.sendEvent(mono)
+			.doOnComplete(() -> {
+				System.out.println("Event handling complete");
+			})
+			.subscribe();
+		// end::snippetB3[]
+	}
+}