requestedHosts.add(hostname)
    return hostAddresses[hostname] ?: throw UnknownHostException()
  }

  fun assertRequests(vararg expectedHosts: String?) {
    assertThat(requestedHosts).containsExactly(*expectedHosts)
    requestedHosts.clear()
  }

  /** Allocates and returns `count` fake IPv4 addresses like [255.0.0.100, 255.0.0.101].  */
  fun allocate(count: Int): List<InetAddress> {

	mgw := MergeGateways(instances, &Proxy{}, nil)
	hosts := mgw.GetAutoPassthrughGatewaySNIHosts()
	expectedHosts := sets.Set[string]{}
	expectedHosts.InsertAll("a.apps.svc.cluster.local", "b.apps.svc.cluster.local")
	if !hosts.Equals(expectedHosts) {
		t.Errorf("expected to get: [a.apps.svc.cluster.local,b.apps.svc.cluster.local], got: %s", hosts.String())
	}
}

	testCases := []struct {
		hostPort     string
		expectedHost string
		expectedPort string
	}{
		{":54321", "", "54321"},
		{"server:54321", "server", "54321"},
		{":0", "", "0"},
		{"server:https", "server", "443"},
		{"server:http", "server", "80"},
	}

	for _, testCase := range testCases {
		host, port := mustSplitHostPort(testCase.hostPort)
		if testCase.expectedHost != host {