Is it possible to use a @Profile("test") configuration to override the default?

We have a spring project which defined some classes without @Profile, like:

interface MyService {
    String changeName(String name);
}

@Service
class MyService1 implements MyService {
    public String changeName(String name) {
        return name.toUpperCase();
    }
}

@Controller
class SampleController {

    @Autowired
    private MyService myService;

    @ResponseBody
    @RequestMapping(value = "/hello/{name}", produces = "application/json")
    String home(@PathVariable String name) {
        return "Hello " + myService.changeName(name) + "!";
    }

}

I can start a server to run it:

@EnableAutoConfiguration
@ComponentScan
@Configuration
public class Main {
    public static void main(String[] args) throws Exception {
        new SpringApplicationBuilder(Main.class)
                .run(args);
    }
}

Then I can visit the url http://localhost:8080/hello/freewind and got the text Hello FREEWIND!.

I want to start a testing server, so I want to find a way to replace the existing MyService1 with a mock class. And I found there is a @Profile seems promissing:

@Profile("test")
@Configuration
class TestConfig {

    @Bean
    public MyService myService() {
        return new MyService() {
            public String changeName(String name) {
                return "###" + name + "###";
            }
        };
    }

}

And change Main to active profile test:

new SpringApplicationBuilder(Main.class)
    .profiles("test")
    .run(args);

But when I start it, it reports error:

Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException:
No qualifying bean of type [web.MyService] is defined: 
expected single matching bean but found 2: myService1,myService

If I want it work, I HAVE to change the existing code to give the MyService1 a different profile, like:

@Profile("dev")
@Configuration
class DevConfig {

    @Bean
    public MyService myService() {
        return new MyService1();
    }

    class MyService1 implements MyService {
        public String changeName(String name) {
            return name.toUpperCase();
        }
    }

}

Now it will work well, but I don't want to modify the existing code.

Is there any way to use @Profile without modifying the existing code, or is there any other way to replace an existing bean with a custom bean?