Add JUnit Jupiter sample application

See gh-8048

spring-boot-samples/spring-boot-sample-junit-jupiter/src/test/java/sample/SampleJunitJupiterApplicationTests.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2012-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sample;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+class SampleJunitJupiterApplicationTests {
+
+	@Autowired
+	private TestRestTemplate restTemplate;
+
+	@Test
+	void testMessage() {
+		String message = this.restTemplate.getForObject("/hi", String.class);
+		assertThat(message).isEqualTo("Hello World");
+	}
+
+}