How to mock a service or stub a service method in a Spring Boot filter using Spock?

Currently i have a filter in my Spring Boot application that uses a Spring service to do some of the heavy lifting stuff..

public class HmacAuthenticationFilter implements Filter {

    @Autowired
    MyService myservice

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        myservice.callMethod();
    }
}

In my Spock test I would like to mock the entire service that the filter uses a stub the myservice.callMethod(); to return a specific value.

Any hints on how this could be done?