Properly assert that auto-configured TaskExecutor is lazy

This commit fixes a flawed assertion that was relying on a log message
to validate the TaskExecutor is lazy. The level of the log message has
changed in framework and broke the test. We now rather check the bean
definition.

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/task/TaskExecutionAutoConfigurationTests.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -23,13 +23,13 @@ import java.util.function.Consumer;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 
+import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.task.TaskExecutorBuilder;
 import org.springframework.boot.task.TaskExecutorCustomizer;
 import org.springframework.boot.test.context.assertj.AssertableApplicationContext;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.boot.test.context.runner.ContextConsumer;
-import org.springframework.boot.test.system.CapturedOutput;
 import org.springframework.boot.test.system.OutputCaptureExtension;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -96,13 +96,13 @@ class TaskExecutionAutoConfigurationTests {
 	}
 
 	@Test
-	void taskExecutorAutoConfigured(CapturedOutput output) {
+	void taskExecutorAutoConfiguredIsLazy() {
 		this.contextRunner.run((context) -> {
-			assertThat(output).doesNotContain("Initializing ExecutorService");
-			assertThat(context).hasSingleBean(Executor.class);
-			assertThat(context).hasBean("applicationTaskExecutor");
+			assertThat(context).hasSingleBean(Executor.class).hasBean("applicationTaskExecutor");
+			BeanDefinition beanDefinition = context.getSourceApplicationContext().getBeanFactory()
+					.getBeanDefinition("applicationTaskExecutor");
+			assertThat(beanDefinition.isLazyInit()).isTrue();
 			assertThat(context).getBean("applicationTaskExecutor").isInstanceOf(ThreadPoolTaskExecutor.class);
-			assertThat(output).contains("Initializing ExecutorService");
 		});
 	}