Settings settings = new Settings();
        Proxy proxy = new Proxy();
        String id = "foo";
        proxy.setId(id);
        proxy.setHost("www.example.com");
        settings.addProxy(proxy);
        settings.addProxy(proxy);

        SimpleProblemCollector problems = new SimpleProblemCollector();
        validator.validate(settings, problems);
        assertEquals(1, problems.messages.size());

     */
    ProfileActivation getProfileActivation();

    // Proxies
    List<Proxy> getProxies();

    MavenExecutionRequest setProxies(List<Proxy> proxies);

    MavenExecutionRequest addProxy(Proxy proxy);

    // Servers
    List<Server> getServers();

    MavenExecutionRequest setServers(List<Server> servers);

    MavenExecutionRequest addServer(Server server);

    // Mirrors

            this.proxies = new ArrayList<>(proxies);
        } else {
            this.proxies = null;
        }

        return this;
    }

    @Override
    public MavenExecutionRequest addProxy(Proxy proxy) {
        Objects.requireNonNull(proxy, "proxy cannot be null");

        for (Proxy p : getProxies()) {
            if (p.getId() != null && p.getId().equals(proxy.getId())) {
                return this;