1 // Copyright 2015 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 BASE_TEST_MOCK_LOG_H_
6 #define BASE_TEST_MOCK_LOG_H_
7 
8 #include <stddef.h>
9 
10 #include <string>
11 
12 #include "base/logging.h"
13 #include "base/macros.h"
14 #include "base/synchronization/lock.h"
15 #include "testing/gmock/include/gmock/gmock.h"
16 
17 namespace base {
18 namespace test {
19 
20 // A MockLog object intercepts LOG() messages issued during its lifespan.  Using
21 // this together with gMock, it's very easy to test how a piece of code calls
22 // LOG().  The typical usage:
23 //
24 //   TEST(FooTest, LogsCorrectly) {
25 //     MockLog log;
26 //
27 //     // We expect the WARNING "Something bad!" exactly twice.
28 //     EXPECT_CALL(log, Log(WARNING, _, "Something bad!"))
29 //         .Times(2);
30 //
31 //     // We allow foo.cc to call LOG(INFO) any number of times.
32 //     EXPECT_CALL(log, Log(INFO, HasSubstr("/foo.cc"), _))
33 //         .Times(AnyNumber());
34 //
35 //     log.StartCapturingLogs();  // Call this after done setting expectations.
36 //     Foo();  // Exercises the code under test.
37 //   }
38 //
39 // CAVEAT: base/logging does not allow a thread to call LOG() again when it's
40 // already inside a LOG() call.  Doing so will cause a deadlock.  Therefore,
41 // it's the user's responsibility to not call LOG() in an action triggered by
42 // MockLog::Log().  You may call RAW_LOG() instead.
43 class MockLog {
44  public:
45   // Creates a MockLog object that is not capturing logs.  If it were to start
46   // to capture logs, it could be a problem if some other threads already exist
47   // and are logging, as the user hasn't had a chance to set up expectation on
48   // this object yet (calling a mock method before setting the expectation is
49   // UNDEFINED behavior).
50   MockLog();
51 
52   // When the object is destructed, it stops intercepting logs.
53   ~MockLog();
54 
55   // Starts log capturing if the object isn't already doing so.
56   // Otherwise crashes.
57   void StartCapturingLogs();
58 
59   // Stops log capturing if the object is capturing logs.  Otherwise crashes.
60   void StopCapturingLogs();
61 
62   // Log method is invoked for every log message before it's sent to other log
63   // destinations (if any).  The method should return true to signal that it
64   // handled the message and the message should not be sent to other log
65   // destinations.
66   MOCK_METHOD5(Log,
67                bool(int severity,
68                     const char* file,
69                     int line,
70                     size_t message_start,
71                     const std::string& str));
72 
73  private:
74   // The currently active mock log.
75   static MockLog* g_instance_;
76 
77   // Lock protecting access to g_instance_.
78   static Lock g_lock;
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 MockLog is destroyed.
92   logging::LogMessageHandlerFunction previous_handler_;
93 
94   DISALLOW_COPY_AND_ASSIGN(MockLog);
95 };
96 
97 }  // namespace test
98 }  // namespace base
99 
100 #endif  // BASE_TEST_MOCK_LOG_H_
101