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());

import java.net.Proxy
import java.net.ProxySelector
import java.net.SocketAddress
import java.net.URI

class FakeProxySelector : ProxySelector() {
  val proxies: MutableList<Proxy> = mutableListOf()

  fun addProxy(proxy: Proxy): FakeProxySelector {
    proxies.add(proxy)
    return this
  }

  override fun select(uri: URI): List<Proxy> {
    // Don't handle 'socket' schemes, which the RI's Socket class may request (for SOCKS).

        for (Proxy proxy : settings.getProxies()) {
            if (!proxy.isActive()) {
                continue;
            }

            proxy = proxy.clone();

            request.addProxy(proxy);
        }

        // <mirrors>
        //   <mirror>
        //     <id>nexus</id>
        //     <mirrorOf>*</mirrorOf>
        //     <url>http://repository.sonatype.org/content/groups/public</url>