Add how to deal with dependencies in scenarios

spring-modulith-examples/spring-modulith-example-epr-jdbc/src/main/resources/application.properties

@@ -1 +1 @@
-spring.modulith.events.jdbc.schema-initialization.enabled=true
+spring.modulith.events.jdbc.schema-initialization.enabled=true

spring-modulith-examples/spring-modulith-example-epr-jdbc/src/test/resources/logback.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+
+	<include resource="org/springframework/boot/logging/logback/defaults.xml"/>
+	<include resource="org/springframework/boot/logging/logback/console-appender.xml" />
+
+	<root level="INFO">
+		<appender-ref ref="CONSOLE" />
+	</root>
+
+	<logger name="org.springframework.modulith" level="WARN"/>
+	<logger name="com.github.dockerjava" level="WARN" />
+	<logger name="example" level="INFO" />
+
+</configuration>

src/docs/asciidoc/30-testing.adoc

@@ -178,6 +178,95 @@ The `result` handed into the `….andVerify(…)` method will be the value retur
 By default, non-`null` values and non-empty ``Optional``s will be considered a conclusive state change.
 This can be tweaked by using the `….andWaitForStateChange(…, Predicate)` overload.
 
+[[testing.scenarios.of.event-driven-modules]]
+=== Integration Test Scenarios of Event-Driven Modules
+
+Consider the following scenario: `order` module publishes an event which is consumed by `inventory` module which in its turn sends another event:
+
+[source, java]
+----
+@Service
+@RequiredArgsConstructor
+public class OrderManagement {
+
+	private final @NonNull ApplicationEventPublisher events;
+
+	@Transactional
+	public void complete(Order order) {
+        // ...
+		events.publishEvent(new OrderCompleted(order.getId()));
+	}
+}
+----
+
+[source, java]
+----
+@Service
+@RequiredArgsConstructor
+class InventoryManagement {
+
+	private final ApplicationEventPublisher events;
+
+	@ApplicationModuleListener
+	void on(OrderCompleted event) {
+        // ...
+		events.publishEvent(new InventoryUpdated(orderId));
+	}
+}
+
+----
+
+If we were to write an integration test which checks that `InventoryUpdated` event is fired after `InventoryManagement` receives `OrderCompleted` in `order` test package, it could look as follows:
+
+[source, java]
+----
+@ApplicationModuleTest(extraIncludes = "inventory")
+@RequiredArgsConstructor
+class OrderManagementTests {
+
+    @Test
+    void inventoryUpdatedIsPublishedOnOrderCompleted(Scenario scenario) {
+        Order order = new Order();
+
+        scenario.publish(new OrderCompleted(order.getId()))
+                .andWaitForEventOfType(InventoryUpdated.class)
+                .toArrive();
+    }
+}
+
+----
+
+Since `order` doesn't have a direct dependency on `inventory` module using `DIRECT_DEPENDENCIES` or `ALL_DEPENDENCIES` bootstrap modes will not import `inventory` module related logic. As a result `InventoryUpdated` event will not be fired and the test will fail.
+In such cases `ApplicationModuleTest` annotation provides `extraIncludes` parameter where extra dependencies may be specified.
+
+One could argue that the above test doesn't really belong to `order` test package but rather it's an application-wide integration test. It could probably be placed directly under the root test package:
+
+[source, java]
+----
+@SpringBootTest
+@EnableScenarios
+class ApplicationIntegrationTests {
+
+    @Test
+    void inventoryUpdatedIsPublishedOnOrderCompleted(Scenario scenario) {
+        Order order = new Order();
+
+        scenario.publish(new OrderCompleted(order.getId()))
+                .andWaitForEventOfType(InventoryUpdated.class)
+                .toArrive();
+    }
+}
+
+----
+
+In such case the combination of `@SpringBootTest` and `@EnableScenarios` can be used (specifying `ApplicationModuleTest` will result in error since the root package is not part of any module).
+
+To summarize when writing integration tests for application modules which interact via events instead of directly depending on another module (via Spring dependency injection mechanisms) Spring Modulith provides
+two options to include dependencies:
+
+* Specifying the dependencies in `extraIncludes` parameter of `@ApplicationModuleTest`
+* Using the combination of `@SpringBootTest` and `@EnableScenarios`
+
 [[testing.scenarios.customize]]
 === Customizing Scenario Execution