I have the following classes:

```
public interface Emailer {}

@Named    
public class RealEmailer implements Emailer {}

@Named
public class NoOpEmailer implements Emailer {}

```

And my service class uses the real emailer:

```
public class SomeService {
    @Inject
    private Emailer emailer;
}

```

The question is, in my service test class (`SomeServiceTest`), how do I inject the `Emailer` in the service to use `NoOpEmailer` ? I'm using Spring for the DI framework.