Test Thymeleaf auto-configuration backs off without spring integration

See gh-16341

Author: snicoll

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/thymeleaf/ThymeleafServletAutoConfigurationTests.java

@@ -38,6 +38,7 @@
 import org.thymeleaf.templateresolver.ITemplateResolver;
 
 import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.test.rule.OutputCapture;
@@ -78,6 +79,14 @@ public class ThymeleafServletAutoConfigurationTests {
 	private final WebApplicationContextRunner contextRunner = new WebApplicationContextRunner()
 			.withConfiguration(AutoConfigurations.of(ThymeleafAutoConfiguration.class));
 
+	@Test
+	public void autoConfigurationBackOffWithoutThymeleafSpring() {
+		this.contextRunner
+				.withClassLoader(new FilteredClassLoader("org.thymeleaf.spring5"))
+				.run((context) -> assertThat(context)
+						.doesNotHaveBean(TemplateEngine.class));
+	}
+
 	@Test
 	public void createFromConfigClass() {
 		this.contextRunner.withPropertyValues("spring.thymeleaf.mode:HTML",