Validate our own tests work with JUnit5 and the vintage engine

Closes gh-14737

Co-authored-by: Stephane Nicoll <snicoll@pivotal.io>

spring-boot-samples/spring-boot-sample-webservices/src/test/java/sample/webservices/SampleWsApplicationTests.java

@@ -21,40 +21,37 @@ import java.io.StringReader;
 import javax.xml.transform.stream.StreamResult;
 import javax.xml.transform.stream.StreamSource;
 
-import org.junit.Before;
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.runner.RunWith;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
 
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
-import org.springframework.boot.test.rule.OutputCapture;
+import org.springframework.boot.test.extension.OutputCapture;
 import org.springframework.boot.web.server.LocalServerPort;
-import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.ws.client.core.WebServiceTemplate;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-@RunWith(SpringRunner.class)
 @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
-public class SampleWsApplicationTests {
+class SampleWsApplicationTests {
 
-	@Rule
-	public final OutputCapture output = new OutputCapture();
+	@RegisterExtension
+	OutputCapture output = new OutputCapture();
 
 	private WebServiceTemplate webServiceTemplate = new WebServiceTemplate();
 
 	@LocalServerPort
 	private int serverPort;
 
-	@Before
+	@BeforeEach
 	public void setUp() {
 		this.webServiceTemplate
 				.setDefaultUri("http://localhost:" + this.serverPort + "/services/");
 	}
 
 	@Test
-	public void testSendingHolidayRequest() {
+	void testSendingHolidayRequest() {
 		final String request = "<hr:HolidayRequest xmlns:hr=\"https://company.example.com/hr/schemas\">"
 				+ "   <hr:Holiday>" + "      <hr:StartDate>2013-10-20</hr:StartDate>"
 				+ "      <hr:EndDate>2013-11-22</hr:EndDate>" + "   </hr:Holiday>"