Prevent making real DNS lookups by chrome tests.

chrome/test/unit/chrome_test_suite.h

 // Copyright (c) 2006-2008 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 CHROME_TEST_UNIT_CHROME_TEST_SUITE_H_
 #define CHROME_TEST_UNIT_CHROME_TEST_SUITE_H_
 
 #include "build/build_config.h"
 
 #include "base/stats_table.h"
 #include "base/file_util.h"
 #if defined(OS_MACOSX)
 #include "base/mac_util.h"
 #endif
 #include "base/path_service.h"
+#include "base/ref_counted.h"
 #include "base/scoped_nsautorelease_pool.h"
 #include "base/test_suite.h"
 #include "chrome/app/scoped_ole_initializer.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/resource_bundle.h"
 #include "chrome/test/testing_browser_process.h"
+#include "net/base/host_resolver_unittest.h"
+
+// In many cases it may be not obvious that a test makes a real DNS lookup.
+// We generally don't want to rely on external DNS servers for our tests,
+// so this mapper catches external queries.
+class WarningHostMapper : public net::HostMapper {
+ public:
+  virtual std::string Map(const std::string& host) {
+    const char* kLocalHostNames[] = {"localhost", "127.0.0.1"};
+    bool local = false;
+    for (size_t i = 0; i < arraysize(kLocalHostNames); i++)
+      if (host == kLocalHostNames[i]) {
+        local = true;
+        break;
+      }
+
+    // Make the test fail so it's harder to ignore.
+    // If you really need to make real DNS query, use net::RuleBasedHostMapper
+    // and its AllowDirectLookup method.
+    EXPECT_TRUE(local) << "Making external DNS lookup of " << host;
+
+    return MapUsingPrevious(host);
+  }
+};
 
 class ChromeTestSuite : public TestSuite {
 public:
   ChromeTestSuite(int argc, char** argv) : TestSuite(argc, argv) {
   }
 
 protected:
 
   virtual void Initialize() {
     base::ScopedNSAutoreleasePool autorelease_pool;
 
     TestSuite::Initialize();
 
+    host_mapper_ = new WarningHostMapper();
+    scoped_host_mapper_.Init(host_mapper_.get());
+
     chrome::RegisterPathProvider();
     g_browser_process = new TestingBrowserProcess;
 
     // Notice a user data override, and otherwise default to using a custom
     // user data directory that lives alongside the current app.
     // NOTE: The user data directory will be erased before each UI test that
     //       uses it, in order to ensure consistency.
     std::wstring user_data_dir =
         CommandLine::ForCurrentProcess()->GetSwitchValue(
             switches::kUserDataDir);
@@ skipping 36 matching lines @@
 
     // Tear down shared StatsTable; prevents unit_tests from leaking it.
     StatsTable::set_current(NULL);
     delete stats_table_;
 
     TestSuite::Shutdown();
   }
 
   StatsTable* stats_table_;
   ScopedOleInitializer ole_initializer_;
+  scoped_refptr<WarningHostMapper> host_mapper_;
+  net::ScopedHostMapper scoped_host_mapper_;
 };
 
 #endif // CHROME_TEST_UNIT_CHROME_TEST_SUITE_H_