Move back to JUnit 4 until SUREFIRE-1614 has been resolved

See gh-14736
See gh-14737
See gh-14738

spring-boot-samples/spring-boot-sample-atmosphere/src/test/java/sample/atmosphere/SampleAtmosphereApplicationTests.java

@@ -22,7 +22,8 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.junit.jupiter.api.Test;
+import org.junit.Test;
+import org.junit.runner.RunWith;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.CommandLineRunner;
@@ -34,6 +35,7 @@ import org.springframework.boot.web.server.LocalServerPort;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.web.socket.TextMessage;
 import org.springframework.web.socket.WebSocketSession;
 import org.springframework.web.socket.client.WebSocketConnectionManager;
@@ -42,6 +44,7 @@ import org.springframework.web.socket.handler.TextWebSocketHandler;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+@RunWith(SpringRunner.class)
 @SpringBootTest(classes = SampleAtmosphereApplication.class, webEnvironment = WebEnvironment.RANDOM_PORT)
 public class SampleAtmosphereApplicationTests {