万能的Hello World

@RestController
public class HelloWorldController {
    @RequestMapping("/")
    public String sayHello() {
        return "Hello World";
    }
}

@SpringBootApplication
public class HelloApplication {
    public static void main(String[] args) {
        SpringApplication.run(HelloApplication.class, args);
    }
}

public class HelloControllerTest {
    @Test
    public void testSayHello() {
        assertEquals("Hello World", new HelloWorldController().sayHello());
    }
}