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// Author: Zhanyong Wan
//
// Defines the ScopedMockLog class (using Google C++ Mocking
// Framework), which is convenient for testing code that uses LOG().
#ifndef GLOG_SRC_MOCK_LOG_H_
#define GLOG_SRC_MOCK_LOG_H_
// For GOOGLE_NAMESPACE. This must go first so we get _XOPEN_SOURCE.
#include "utilities.h"
#include <string>
#include <gmock/gmock.h>
#include "glog/logging.h"
_START_GOOGLE_NAMESPACE_
namespace glog_testing {
// A ScopedMockLog object intercepts LOG() messages issued during its
// lifespan. Using this together with Google C++ Mocking Framework,
// it's very easy to test how a piece of code calls LOG(). The
// typical usage:
//
// TEST(FooTest, LogsCorrectly) {
// ScopedMockLog 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());
//
// Foo(); // Exercises the code under test.
// }
class ScopedMockLog : public GOOGLE_NAMESPACE::LogSink {
public:
// When a ScopedMockLog object is constructed, it starts to
// intercept logs.
ScopedMockLog() { AddLogSink(this); }
// When the object is destructed, it stops intercepting logs.
virtual ~ScopedMockLog() { RemoveLogSink(this); }
// Implements the mock method:
//
// void Log(LogSeverity severity, const string& file_path,
// const string& message);
//
// The second argument to Send() is the full path of the source file
// in which the LOG() was issued.
//
// Note, that in a multi-threaded environment, all LOG() messages from a
// single thread will be handled in sequence, but that cannot be guaranteed
// for messages from different threads. In fact, if the same or multiple
// expectations are matched on two threads concurrently, their actions will
// be executed concurrently as well and may interleave.
MOCK_METHOD3(Log, void(GOOGLE_NAMESPACE::LogSeverity severity,
const std::string& file_path,
const std::string& message));
private:
// Implements the send() virtual function in class LogSink.
// Whenever a LOG() statement is executed, this function will be
// invoked with information presented in the LOG().
//
// The method argument list is long and carries much information a
// test usually doesn't care about, so we trim the list before
// forwarding the call to Log(), which is much easier to use in
// tests.
//
// We still cannot call Log() directly, as it may invoke other LOG()
// messages, either due to Invoke, or due to an error logged in
// Google C++ Mocking Framework code, which would trigger a deadlock
// since a lock is held during send().
//
// Hence, we save the message for WaitTillSent() which will be called after
// the lock on send() is released, and we'll call Log() inside
// WaitTillSent(). Since while a single send() call may be running at a
// time, multiple WaitTillSent() calls (along with the one send() call) may
// be running simultaneously, we ensure thread-safety of the exchange between
// send() and WaitTillSent(), and that for each message, LOG(), send(),
// WaitTillSent() and Log() are executed in the same thread.
virtual void send(GOOGLE_NAMESPACE::LogSeverity severity,
const char* full_filename,
const char* /*base_filename*/, int /*line*/,
const tm* /*tm_time*/,
const char* message, size_t message_len) {
// We are only interested in the log severity, full file name, and
// log message.
message_info_.severity = severity;
message_info_.file_path = full_filename;
message_info_.message = std::string(message, message_len);
}
// Implements the WaitTillSent() virtual function in class LogSink.
// It will be executed after send() and after the global logging lock is
// released, so calls within it (or rather within the Log() method called
// within) may also issue LOG() statements.
//
// LOG(), send(), WaitTillSent() and Log() will occur in the same thread for
// a given log message.
virtual void WaitTillSent() {
// First, and very importantly, we save a copy of the message being
// processed before calling Log(), since Log() may indirectly call send()
// and WaitTillSent() in the same thread again.
MessageInfo message_info = message_info_;
Log(message_info.severity, message_info.file_path, message_info.message);
}
// All relevant information about a logged message that needs to be passed
// from send() to WaitTillSent().
struct MessageInfo {
GOOGLE_NAMESPACE::LogSeverity severity;
std::string file_path;
std::string message;
};
MessageInfo message_info_;
};
} // namespace glog_testing
_END_GOOGLE_NAMESPACE_
#endif // GLOG_SRC_MOCK_LOG_H_
