net/test/scoped_mock_log.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_QUIC_TEST_TOOLS_SCOPED_MOCK_LOG_H_
   6 #define NET_QUIC_TEST_TOOLS_SCOPED_MOCK_LOG_H_
   7
   8 #include "base/logging.h"
   9 #include "testing/gmock/include/gmock/gmock.h"
  10 #include "testing/gtest/include/gtest/gtest.h"
  11
  12 namespace net {
  13 namespace test {
  14
  15 // A ScopedMockLog object intercepts LOG() messages issued during its
  16 // lifespan.  Using this together with gMock, it's very easy to test
  17 // how a piece of code calls LOG().  The typical usage:
  18 //
  19 //   TEST(FooTest, LogsCorrectly) {
  20 //     ScopedMockLog log;
  21 //
  22 //     // We expect the WARNING "Something bad!" exactly twice.
  23 //     EXPECT_CALL(log, Log(WARNING, _, "Something bad!"))
  24 //         .Times(2);
  25 //
  26 //     // We allow foo.cc to call LOG(INFO) any number of times.
  27 //     EXPECT_CALL(log, Log(INFO, HasSubstr("/foo.cc"), _))
  28 //         .Times(AnyNumber());
  29 //
  30 //     log.StartCapturingLogs();  // Call this after done setting expectations.
  31 //     Foo();  // Exercises the code under test.
  32 //   }
  33 //
  34 // CAVEAT: base/logging does not allow a thread to call LOG() again
  35 // when it's already inside a LOG() call.  Doing so will cause a
  36 // deadlock.  Therefore, it's the user's responsibility to not call
  37 // LOG() in an action triggered by ScopedMockLog::Log().  You may call
  38 // RAW_LOG() instead.
  39 class ScopedMockLog {
  40  public:
  41   // Creates a ScopedMockLog object that is not capturing logs.
  42   // If it were to start to capture logs, it could be a problem if
  43   // some other threads already exist and are logging, as the user
  44   // hasn't had a chance to set up expectation on this object yet
  45   // (calling a mock method before setting the expectation is
  46   // UNDEFINED behavior).
  47   ScopedMockLog();
  48
  49   // When the object is destructed, it stops intercepting logs.
  50   ~ScopedMockLog();
  51
  52   // Starts log capturing if the object isn't already doing so.
  53   // Otherwise crashes.  Usually this method is called in the same
  54   // thread that created this object.  It is the user's responsibility
  55   // to not call this method if another thread may be calling it or
  56   // StopCapturingLogs() at the same time.
  57   void StartCapturingLogs();
  58
  59   // Stops log capturing if the object is capturing logs.  Otherwise
  60   // crashes.  Usually this method is called in the same thread that
  61   // created this object.  It is the user's responsibility to not call
  62   // this method if another thread may be calling it or
  63   // StartCapturingLogs() at the same time.
  64   void StopCapturingLogs();
  65
  66   // Sets the Log Message Handler that gets passed every log message before
  67   // it's sent to other log destinations (if any).
  68   // Returns true to signal that it handled the message and the message
  69   // should not be sent to other log destinations.
  70   MOCK_METHOD5(Log, bool(int severity,
  71                          const char* file,
  72                          int line,
  73                          size_t message_start,
  74                          const std::string& str));
  75
  76  private:
  77   // The currently active scoped mock log.
  78   static ScopedMockLog* g_instance_;
  79
  80   // Static function which is set as the logging message handler.
  81   // Called once for each message.
  82   static bool LogMessageHandler(int severity,
  83                                 const char* file,
  84                                 int line,
  85                                 size_t message_start,
  86                                 const std::string& str);
  87
  88   // True if this object is currently capturing logs.
  89   bool is_capturing_logs_;
  90
  91   // The previous handler to restore when the ScopedMockLog is destroyed.
  92   logging::LogMessageHandlerFunction previous_handler_;
  93 };
  94
  95 }  // namespace test
  96 }  // namespace net
  97
  98 #endif  // NET_QUIC_TEST_TOOLS_SCOPED_MOCK_LOG_H_