Align test expectations with styling of stack trace div

Closes gh-15075

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/error/DefaultErrorWebExceptionHandlerIntegrationTests.java

@@ -195,8 +195,8 @@ public class DefaultErrorWebExceptionHandlerIntegrationTests {
 							.contentType(MediaType.TEXT_HTML).expectBody(String.class)
 							.returnResult().getResponseBody();
 					assertThat(body).contains("Whitelabel Error Page")
-							.contains("<div>Expected!</div>")
-							.contains("<div>java.lang.IllegalStateException");
+							.contains("<div>Expected!</div>").contains(
+									"<div style='white-space:pre-wrap;'>java.lang.IllegalStateException");
 				});
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/error/ErrorMvcAutoConfigurationTests.java

@@ -60,8 +60,8 @@ public class ErrorMvcAutoConfigurationTests {
 					.getContentAsString();
 			assertThat(responseString).contains(
 					"<p>This application has no explicit mapping for /error, so you are seeing this as a fallback.</p>")
-					.contains("<div>Exception message</div>")
-					.contains("<div>java.lang.IllegalStateException");
+					.contains("<div>Exception message</div>").contains(
+							"<div style='white-space:pre-wrap;'>java.lang.IllegalStateException");
 		});
 	}