GH-190 - Introduce @EnableScenarios.

The dedicated annotation allows using Scenario as test parameter in @SpringBootTest-based integration tests, too.

ScenarioParameterResolver now throws a better error message if a TransactionTemplate bean is missing from the ApplicationContext.

spring-modulith-test/src/main/java/org/springframework/modulith/test/EnableScenarios.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2023 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.modulith.test;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+
+/**
+ * Allows using {@link Scenario} as method parameter in integration tests.
+ *
+ * @author Oliver Drotbohm
+ * @see Scenario
+ */
+@Documented
+@Inherited
+@Target(value = ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@ExtendWith(ScenarioParameterResolver.class)
+public @interface EnableScenarios {}

spring-modulith-test/src/main/java/org/springframework/modulith/test/ScenarioParameterResolver.java

@@ -20,6 +20,8 @@ import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ParameterContext;
 import org.junit.jupiter.api.extension.ParameterResolutionException;
 import org.junit.jupiter.api.extension.ParameterResolver;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.context.ApplicationContext;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
 import org.springframework.transaction.support.TransactionTemplate;
 
@@ -30,6 +32,8 @@ import org.springframework.transaction.support.TransactionTemplate;
  */
 class ScenarioParameterResolver implements ParameterResolver, BeforeAllCallback {
 
+	private static final String MISSING_TRANSACTION_TEMPLATE = "To use a Scenario in an integration test you need to define a bean of type TransactionTemplate! Please check your ApplicationContext setup.";
+
 	private final PublishedEventsParameterResolver delegate;
 
 	/**
@@ -70,9 +74,18 @@ class ScenarioParameterResolver implements ParameterResolver, BeforeAllCallback
 			throws ParameterResolutionException {
 
 		var context = SpringExtension.getApplicationContext(extensionContext);
-		var operations = context.getBean(TransactionTemplate.class);
+		var operations = resolveTransactionTemplate(context);
 		var events = (AssertablePublishedEvents) delegate.resolveParameter(parameterContext, extensionContext);
 
 		return new Scenario(operations, context, events);
 	}
+
+	private TransactionTemplate resolveTransactionTemplate(ApplicationContext context) {
+
+		try {
+			return context.getBean(TransactionTemplate.class);
+		} catch (NoSuchBeanDefinitionException o_O) {
+			throw new ParameterResolutionException(MISSING_TRANSACTION_TEMPLATE, o_O);
+		}
+	}
 }