Add more unit tests for net/base/host_resolver.

net/base/host_resolver_unittest.h

+// Copyright (c) 2006-2009 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_BASE_HOST_RESOLVER_UNITTEST_H_
+#define NET_BASE_HOST_RESOLVER_UNITTEST_H_
+
+#ifdef UNIT_TEST
+
+#include <list>
+
+#include "base/string_util.h"
+#include "base/platform_thread.h"
+#include "base/ref_counted.h"
+#include "base/waitable_event.h"
+#include "net/base/host_resolver.h"
+#include "net/base/net_errors.h"
+
+namespace net {
+
+// In most cases, it is important that unit tests avoid making actual DNS
+// queries since the resulting tests can be flaky, especially if the network is
+// unreliable for some reason.  To simplify writing tests that avoid making
+// actual DNS queries, the following helper class may be used:
+//
+//   scoped_refptr<RuleBasedHostMapper> host_mapper = new RuleBasedHostMapper();
+//   host_mapper->AddRule("foo.com", "1.2.3.4");
+//   host_mapper->AddRule("bar.com", "2.3.4.5");
+//
+// Don't forget to actually set your mapper, probably with ScopedHostMapper!
+//
+// The above rules define a static mapping from hostnames to IP address
+// literals.  The first parameter to AddRule specifies a host pattern to match
+// against, and the second parameter indicates what value should be used to
+// replace the given hostname.  So, the following is also supported:
+//
+//   host_mapper->AddRule("*.com", "127.0.0.1");
+//
+// Replacement doesn't have to be string representing an IP address. It can
+// re-map one hostname to another as well.
+class RuleBasedHostMapper : public HostMapper {
+ public:
+  // Any hostname matching the given pattern will be replaced with the given
+  // replacement value.  Usually, replacement should be an IP address literal.
+  void AddRule(const char* host_pattern, const char* replacement) {
+    rules_.push_back(Rule(host_pattern, replacement));
+  }
+
+  void AddRuleWithLatency(const char* host_pattern, const char* replacement,
+                          int latency) {
+    rules_.push_back(Rule(host_pattern, replacement, latency));
+  }
+
+ private:
+  std::string Map(const std::string& host) {
+    RuleList::iterator r;
+    for (r = rules_.begin(); r != rules_.end(); ++r) {
+      if (MatchPattern(host, r->host_pattern)) {
+        if (r->latency != 0) {
+          PlatformThread::Sleep(r->latency);
+          r->latency = 1;  // Simulate cache warmup.
+        }
+        return r->replacement;
+      }
+    }
+    return MapUsingPrevious(host);
+  }
+
+  struct Rule {
+    std::string host_pattern;
+    std::string replacement;
+    int latency;  // in milliseconds
+    Rule(const char* h, const char* r)
+        : host_pattern(h),
+          replacement(r),
+          latency(0) {}
+    Rule(const char* h, const char* r, const int l)
+        : host_pattern(h),
+          replacement(r),
+          latency(l) {}
+  };
+  typedef std::list<Rule> RuleList;
+
+  RuleList rules_;
+};
+
+// Using WaitingHostMapper you can simulate very long lookups, for example
+// to test code which cancels a request. Example usage:
+//
+//   scoped_refptr<WaitingHostMapper> mapper = new WaitingHostMapper();
+//   ScopedHostMapper scoped_mapper(mapper.get());
+//
+//   (start the lookup asynchronously)
+//   (cancel the lookup)
+//
+//   mapper->Signal();
+class WaitingHostMapper : public HostMapper {
+ public:
+  WaitingHostMapper() : event_(false, false) {
+  }
+
+  void Signal() {
+    event_.Signal();
+  }
+
+ private:
+  std::string Map(const std::string& host) {
+    event_.Wait();
+    return MapUsingPrevious(host);
+  }
+
+  base::WaitableEvent event_;
+};
+
+// This class sets the HostMapper for a particular scope. If there are multiple
+// ScopedHostMappers in existence, then the last one allocated will be used.
+// However, if it does not provide a matching rule, then it should delegate
+// to the previously set HostMapper (see SetHostMapper). This is true for all
+// mappers defined in this file. If no HostMapper matches a given hostname, then
+// the hostname will be unmodified.
+class ScopedHostMapper {
+ public:
+  ScopedHostMapper(HostMapper* mapper) : current_host_mapper_(mapper) {
+    previous_host_mapper_ = SetHostMapper(current_host_mapper_.get());
+    current_host_mapper_->set_previous_mapper(previous_host_mapper_.get());
+  }
+
+  ~ScopedHostMapper() {
+    HostMapper* old_mapper = SetHostMapper(previous_host_mapper_.get());
+    // The lifetimes of multiple instances must be nested.
+    CHECK(old_mapper == current_host_mapper_.get());
+  }
+
+ private:
+  scoped_refptr<HostMapper> current_host_mapper_;
+  scoped_refptr<HostMapper> previous_host_mapper_;
+};
+
+}  // namespace net
+
+#endif  // UNIT_TEST
+
+#endif  // NET_BASE_HOST_RESOLVER_UNITTEST_H_