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-simple/src/test/java/sample/simple/SampleSimpleApplicationTests.java

@@ -16,12 +16,12 @@
 
 package sample.simple;
 
-import org.junit.After;
-import org.junit.Before;
-import org.junit.Rule;
-import org.junit.Test;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
 
-import org.springframework.boot.test.rule.OutputCapture;
+import org.springframework.boot.test.extension.OutputCapture;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -31,19 +31,19 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Dave Syer
  * @author Phillip Webb
  */
-public class SampleSimpleApplicationTests {
+class SampleSimpleApplicationTests {
 
-	@Rule
-	public final OutputCapture output = new OutputCapture();
+	@RegisterExtension
+	OutputCapture output = new OutputCapture();
 
 	private String profiles;
 
-	@Before
+	@BeforeEach
 	public void init() {
 		this.profiles = System.getProperty("spring.profiles.active");
 	}
 
-	@After
+	@AfterEach
 	public void after() {
 		if (this.profiles != null) {
 			System.setProperty("spring.profiles.active", this.profiles);
@@ -54,14 +54,14 @@ public class SampleSimpleApplicationTests {
 	}
 
 	@Test
-	public void testDefaultSettings() throws Exception {
+	void testDefaultSettings() throws Exception {
 		SampleSimpleApplication.main(new String[0]);
 		String output = this.output.toString();
 		assertThat(output).contains("Hello Phil");
 	}
 
 	@Test
-	public void testCommandLineOverrides() throws Exception {
+	void testCommandLineOverrides() throws Exception {
 		SampleSimpleApplication.main(new String[] { "--name=Gordon", "--duration=1m" });
 		String output = this.output.toString();
 		assertThat(output).contains("Hello Gordon for 60 seconds");

spring-boot-samples/spring-boot-sample-simple/src/test/java/sample/simple/SpringTestSampleSimpleApplicationTests.java

@@ -16,13 +16,11 @@
 
 package sample.simple;
 
-import org.junit.Test;
-import org.junit.runner.RunWith;
+import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.context.ApplicationContext;
-import org.springframework.test.context.junit4.SpringRunner;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -31,15 +29,14 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Dave Syer
  */
-@RunWith(SpringRunner.class)
 @SpringBootTest
-public class SpringTestSampleSimpleApplicationTests {
+class SpringTestSampleSimpleApplicationTests {
 
 	@Autowired
 	ApplicationContext ctx;
 
 	@Test
-	public void testContextLoads() {
+	void testContextLoads() {
 		assertThat(this.ctx).isNotNull();
 		assertThat(this.ctx.containsBean("helloWorldService")).isTrue();
 		assertThat(this.ctx.containsBean("sampleSimpleApplication")).isTrue();