testserver.py listens on ephemeral ports by default.

net/test/test_server.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_TEST_TEST_SERVER_H_
 #define NET_TEST_TEST_SERVER_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 95 matching lines @@
              const FilePath& document_root);
 
   ~TestServer();
 
   bool Start() WARN_UNUSED_RESULT;
 
   // Stop the server started by Start().
   bool Stop();
 
   const FilePath& document_root() const { return document_root_; }
-  const HostPortPair& host_port_pair() const { return host_port_pair_; }
+  const HostPortPair& host_port_pair() const;
   std::string GetScheme() const;
   bool GetAddressList(AddressList* address_list) const WARN_UNUSED_RESULT;
 
   GURL GetURL(const std::string& path);
 
   GURL GetURLWithUser(const std::string& path,
                       const std::string& user);
 
   GURL GetURLWithUserAndPassword(const std::string& path,
                                  const std::string& user,
@@ skipping 55 matching lines @@
 
   // If |type_| is TYPE_HTTPS, the TLS settings to use for the test server.
   HTTPSOptions https_options_;
 
 #if defined(USE_NSS)
   scoped_refptr<X509Certificate> cert_;
 #endif
 
   Type type_;
 
+  // Has the server been started?
+  bool started_;
+
   DISALLOW_COPY_AND_ASSIGN(TestServer);
 };
 
 }  // namespace net
 
 #endif  // NET_TEST_TEST_SERVER_H_