GH-165 - Introduce ScenarioCustomizer extension.

We now provide a ScenarioCustomizer that can be used to prepare Scenario instances for test methods with a common customizer. This avoids the need to call ….customize(…) for all Scenarios declared in a test class with the same logic.

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

@@ -74,6 +74,8 @@ public class Scenario {
 	private final ApplicationEventPublisher publisher;
 	private final AssertablePublishedEvents events;
 
+	private Function<ConditionFactory, ConditionFactory> defaultCustomizer;
+
 	/**
 	 * Creates a new {@link Scenario} for the given {@link TransactionTemplate}, {@link ApplicationEventPublisher} and
 	 * {@link AssertablePublishedEvents}.
@@ -95,6 +97,7 @@ public class Scenario {
 		this.transactionOperations = new TransactionTemplate(transactionTemplate.getTransactionManager(), definition);
 		this.publisher = publisher;
 		this.events = events;
+		this.defaultCustomizer = Function.identity();
 	}
 
 	/**
@@ -197,7 +200,22 @@ public class Scenario {
 
 		Assert.notNull(stimulus, "Stimulus must not be null!");
 
-		return new When<>(stimulus, __ -> {}, Function.identity());
+		return new When<>(stimulus, __ -> {}, defaultCustomizer);
+	}
+
+	/**
+	 * Extension hook to allow registration of a global customizer. If none configured we will fall back to
+	 * {@link Function#identity()}.
+	 *
+	 * @param customizer must not be {@literal null}.
+	 * @see org.springframework.modulith.test.ScenarioCustomizer
+	 */
+	Scenario setDefaultCustomizer(Function<ConditionFactory, ConditionFactory> customizer) {
+
+		Assert.notNull(customizer, "Customizer must not be null!");
+
+		this.defaultCustomizer = customizer;
+		return this;
 	}
 
 	public class When<T> {
@@ -263,6 +281,10 @@ public class Scenario {
 		}
 
 		/**
+		 * Customize the execution of the scenario. The given customizer will be added to the default one registered via a
+		 * {@link org.springframework.modulith.test.ScenarioCustomizer}. In other words, multiple invocations will replace
+		 * registrations made in previous calls but always be chained after the default customizations registered.
+		 *
 		 * @param customizer must not be {@literal null}.
 		 * @return will never be {@literal null}.
 		 */
@@ -270,7 +292,7 @@ public class Scenario {
 
 			Assert.notNull(customizer, "Customizer must not be null!");
 
-			return new When<T>(stimulus, cleanup, customizer);
+			return new When<T>(stimulus, cleanup, defaultCustomizer.andThen(customizer));
 		}
 
 		// Expect event

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

@@ -0,0 +1,100 @@
+/*
+ * 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.reflect.Method;
+import java.util.function.Function;
+
+import org.awaitility.core.ConditionFactory;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.api.extension.InvocationInterceptor;
+import org.junit.jupiter.api.extension.ReflectiveInvocationContext;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.util.Assert;
+
+/**
+ * A JUnit {@link InvocationInterceptor} to register a default customizer to be applied to all {@link Scenario}
+ * instances associated with that test case.
+ *
+ * @author Oliver Drotbohm
+ */
+public interface ScenarioCustomizer extends InvocationInterceptor {
+
+	/**
+	 * Return a customizer to be applied to the {@link Scenario} instance handed into the given method.
+	 *
+	 * @param method will never be {@literal null}.
+	 * @param context will never be {@literal null}.
+	 * @return must not be {@literal null}.
+	 */
+	Function<ConditionFactory, ConditionFactory> getDefaultCustomizer(Method method, ApplicationContext context);
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.junit.jupiter.api.extension.InvocationInterceptor#interceptTestTemplateMethod(org.junit.jupiter.api.extension.InvocationInterceptor.Invocation, org.junit.jupiter.api.extension.ReflectiveInvocationContext, org.junit.jupiter.api.extension.ExtensionContext)
+	 */
+	@Override
+	default void interceptTestTemplateMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext, ExtensionContext extensionContext) throws Throwable {
+
+		prepareScenarioInstance(invocationContext, extensionContext);
+
+		invocation.proceed();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.junit.jupiter.api.extension.InvocationInterceptor#interceptTestFactoryMethod(org.junit.jupiter.api.extension.InvocationInterceptor.Invocation, org.junit.jupiter.api.extension.ReflectiveInvocationContext, org.junit.jupiter.api.extension.ExtensionContext)
+	 */
+	@Override
+	default <T> T interceptTestFactoryMethod(Invocation<T> invocation,
+			ReflectiveInvocationContext<Method> invocationContext, ExtensionContext extensionContext) throws Throwable {
+
+		prepareScenarioInstance(invocationContext, extensionContext);
+
+		return invocation.proceed();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.junit.jupiter.api.extension.InvocationInterceptor#interceptTestMethod(org.junit.jupiter.api.extension.InvocationInterceptor.Invocation, org.junit.jupiter.api.extension.ReflectiveInvocationContext, org.junit.jupiter.api.extension.ExtensionContext)
+	 */
+	@Override
+	default void interceptTestMethod(Invocation<Void> invocation, ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) throws Throwable {
+
+		prepareScenarioInstance(invocationContext, extensionContext);
+
+		invocation.proceed();
+	}
+
+	private void prepareScenarioInstance(ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) {
+
+		invocationContext.getArguments().stream()
+				.filter(Scenario.class::isInstance)
+				.map(Scenario.class::cast)
+				.forEach(it -> {
+
+					var context = SpringExtension.getApplicationContext(extensionContext);
+					var customizer = getDefaultCustomizer(invocationContext.getExecutable(), context);
+					Assert.state(customizer != null, "Customizer must not be null!");
+
+					it.setDefaultCustomizer(customizer);
+				});
+	}
+}