text: // Copyright 2015 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 BASE_TEST_MOCK_LOG_H_
  #define BASE_TEST_MOCK_LOG_H_
  
  #include <stddef.h>
  
  #include <string>
  
  #include "base/logging.h"
  #include "base/macros.h"
  #include "base/synchronization/lock.h"
  #include "testing/gmock/include/gmock/gmock.h"
  
  namespace base {
  namespace test {
  
  // A MockLog object intercepts LOG() messages issued during its lifespan.  Using
  // this together with gMock, it's very easy to test how a piece of code calls
  // LOG().  The typical usage:
  //
  //   TEST(FooTest, LogsCorrectly) {
  //     MockLog log;
  //
  //     // We expect the WARNING "Something bad!" exactly twice.
  //     EXPECT_CALL(log, Log(WARNING, _, "Something bad!"))
  //         .Times(2);
  //
  //     // We allow foo.cc to call LOG(INFO) any number of times.
  //     EXPECT_CALL(log, Log(INFO, HasSubstr("/foo.cc"), _))
  //         .Times(AnyNumber());
  //
  //     log.StartCapturingLogs();  // Call this after done setting expectations.
  //     Foo();  // Exercises the code under test.
  //   }
  //
  // CAVEAT: base/logging does not allow a thread to call LOG() again when it's
  // already inside a LOG() call.  Doing so will cause a deadlock.  Therefore,
  // it's the user's responsibility to not call LOG() in an action triggered by
  // MockLog::Log().  You may call RAW_LOG() instead.
  class MockLog {
   public:
    // Creates a MockLog object that is not capturing logs.  If it were to start
    // to capture logs, it could be a problem if some other threads already exist
    // and are logging, as the user hasn't had a chance to set up expectation on
    // this object yet (calling a mock method before setting the expectation is
    // UNDEFINED behavior).
    MockLog();
  
    // When the object is destructed, it stops intercepting logs.
    ~MockLog();
  
    // Starts log capturing if the object isn't already doing so.
    // Otherwise crashes.
    void StartCapturingLogs();
  
    // Stops log capturing if the object is capturing logs.  Otherwise crashes.
    void StopCapturingLogs();
  
    // Log method is invoked for every log message before it's sent to other log
    // destinations (if any).  The method should return true to signal that it
    // handled the message and the message should not be sent to other log
    // destinations.
    MOCK_METHOD5(Log,
                 bool(int severity,
                      const char* file,
                      int line,
                      size_t message_start,
                      const std::string& str));
  
   private:
    // The currently active mock log.
    static MockLog* g_instance_;
  
    // Lock protecting access to g_instance_.
    static Lock g_lock;
  
    // Static function which is set as the logging message handler.
    // Called once for each message.
    static bool LogMessageHandler(int severity,
                                  const char* file,
                                  int line,
                                  size_t message_start,
                                  const std::string& str);
  
    // True if this object is currently capturing logs.
    bool is_capturing_logs_;
  
    // The previous handler to restore when the MockLog is destroyed.
    logging::LogMessageHandlerFunction previous_handler_;
  
    DISALLOW_COPY_AND_ASSIGN(MockLog);
  };
  
  }  // namespace test
  }  // namespace base
  
  #endif  // BASE_TEST_MOCK_LOG_H_
  