Polish test

Include at least a bean declaration to make sure the cglib proxy is
created

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/SpringApplicationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -1588,6 +1588,11 @@ class SpringApplicationTests {
 		private InaccessibleConfiguration() {
 		}
 
+		@Bean
+		String testMessage() {
+			return "test";
+		}
+
 	}
 
 	static class SpyApplicationContext extends AnnotationConfigApplicationContext {