GTest源码剖析（七）——断言

GTest源码剖析——断言

1 ASSERT_TRUE宏

ASSERT_TRUE宏和ASSERT_FALSE宏几乎认为无区别，仅仅是参数取反而已。

ASSERT_*宏定义如下：

#define ASSERT_TRUE(condition)   GTEST_TEST_BOOLEAN_((condition), #condition, false, true, GTEST_FATAL_FAILURE_)#define ASSERT_FALSE(condition)   GTEST_TEST_BOOLEAN_(!(condition), #condition, true, false, GTEST_FATAL_FAILURE_)

1.1 ASSERT_TRUE宏 和 EXPECT_TRUE宏 的区别

1. EXPECT_TRUE宏和ASSERT_FALSE宏 几乎认为无区别，仅仅是参数取反而已；

2. EXPECT_TRUE宏和ASSERT_FALSE宏 均使用GTEST_TEST_BOOLEAN_宏；
   两者的区别仅仅是第五个参数不同
   EXPECT_TRUE的参数是GTEST_NONFATAL_FAILURE_，而ASSERT_TRUE的参数是GTEST_FATAL_FAILURE_

EXPECT_*宏定义如下：

#define EXPECT_TRUE(condition)   GTEST_TEST_BOOLEAN_((condition), #condition, false, true,GTEST_NONFATAL_FAILURE_)#define EXPECT_FALSE(condition)   GTEST_TEST_BOOLEAN_(!(condition), #condition, true, false, GTEST_NONFATAL_FAILURE_)

3.对比一下 GTEST_FATAL_FAILURE_宏 和 GTEST_NONFATAL_FAILURE_宏 的区别可以发现，两者均使用GTEST_MESSAGE_宏，
区别在于使用了不同的TestPartResult的枚举值。

宏定义如下：

#define GTEST_FATAL_FAILURE_(message)   return GTEST_MESSAGE_(message, ::testing::TestPartResult::kFatalFailure)#define GTEST_NONFATAL_FAILURE_(message)   GTEST_MESSAGE_(message, ::testing::TestPartResult::kNonFatalFailure)

TestPartResult类定义如下，仅仅是定义了三个枚举值而已。

class GTEST_API_ TestPartResult {public:  enum Type   {    kSuccess,          // Succeeded.    kNonFatalFailure,  // Failed but the test can continue.    kFatalFailure      // Failed and the test should be terminated.  };

1.1.1 GTEST_MESSAGE_宏

1. GTEST_MESSAGE_宏定义如下：

#define GTEST_MESSAGE_(message, result_type)   GTEST_MESSAGE_AT_(__FILE__, __LINE__, message, result_type)

1. GTEST_MESSAGE_AT_宏定义如下：

#define GTEST_MESSAGE_AT_(file, line, message, result_type)   ::testing::internal::AssertHelper(result_type, file, line, message)     = ::testing::Message()

1.1.2 AssertHelper类

重载了void operator=(const Message& message) const;利用它把断言的结果信息添加到TestResult中。

class GTEST_API_ AssertHelper {public:  AssertHelper(TestPartResult::Type type, const char* file, int line, const char* message);  ~AssertHelper();  void operator=(const Message& message) const;private:  struct AssertHelperData   {    AssertHelperData(TestPartResult::Type t,                     const char* srcfile,                     int line_num,                     const char* msg)        : type(t), file(srcfile), line(line_num), message(msg) { }    TestPartResult::Type const type;    const char* const file;    int const line;    std::string const message;   private:    GTEST_DISALLOW_COPY_AND_ASSIGN_(AssertHelperData);  };  AssertHelperData* const data_;  GTEST_DISALLOW_COPY_AND_ASSIGN_(AssertHelper);};// AssertHelper constructor.AssertHelper::AssertHelper(TestPartResult::Type type,                           const char* file,                           int line,                           const char* message)    : data_(new AssertHelperData(type, file, line, message)) {}AssertHelper::~AssertHelper() {  delete data_;}// Message assignment, for assertion streaming support.void AssertHelper::operator=(const Message& message) const {  UnitTest::GetInstance()->    AddTestPartResult(data_->type, data_->file, data_->line,                      AppendUserMessage(data_->message, message),                      UnitTest::GetInstance()->impl()                      ->CurrentOsStackTraceExceptTop(1)                      // Skips the stack frame for this function itself.                      );  // NOLINT}

UnitTest::AddTestPartResult

void UnitTest::AddTestPartResult(    TestPartResult::Type result_type,    const char* file_name,    int line_number,    const std::string& message,    const std::string& os_stack_trace) {  Message msg;  msg << message;  internal::MutexLock lock(&mutex_);  if (impl_->gtest_trace_stack().size() > 0)   {    msg << "\n" << GTEST_NAME_ << " trace:";    for (int i = static_cast<int>(impl_->gtest_trace_stack().size()); i > 0; --i)     {      const internal::TraceInfo& trace = impl_->gtest_trace_stack()[i - 1];      msg << "\n" << internal::FormatFileLocation(trace.file, trace.line)          << " " << trace.message;    }  }}

1.2 ASSERT_TRUE宏的实现

#define GTEST_TEST_BOOLEAN_(expression, text, actual, expected, fail)   GTEST_AMBIGUOUS_ELSE_BLOCKER_   if (const ::testing::AssertionResult gtest_ar_ =       ::testing::AssertionResult(expression))     ;   else     fail(::testing::internal::GetBoolAssertionFailureMessage(        gtest_ar_, text, #actual, #expected).c_str())

1.2.1 AssertionResult类

class GTEST_API_ AssertionResult {public:  AssertionResult(const AssertionResult& other);  GTEST_DISABLE_MSC_WARNINGS_PUSH_(4800 /* forcing value to bool */)  template <typename T>  explicit AssertionResult(      const T& success,      typename internal::EnableIf<          !internal::ImplicitlyConvertible<T, AssertionResult>::value>::type*          /*enabler*/ = NULL)      : success_(success) {}  GTEST_DISABLE_MSC_WARNINGS_POP_()  // Assignment operator.  AssertionResult& operator=(AssertionResult other)   {    swap(other);    return *this;  }  operator bool() const { return success_; }   AssertionResult operator!() const;  const char* message() const   {    return message_.get() != NULL ?  message_->c_str() : "";  }  template <typename T> AssertionResult& operator<<(const T& value)   {    AppendMessage(Message() << value);    return *this;  }  AssertionResult& operator<<(std::ostream& (*basic_manipulator)(::std::ostream& stream))   {    AppendMessage(Message() << basic_manipulator);    return *this;  }private:  void AppendMessage(const Message& a_message)   {    if (message_.get() == NULL)      message_.reset(new ::std::string);    message_->append(a_message.GetString().c_str());  }  void swap(AssertionResult& other);  internal::scoped_ptr< ::std::string> message_;};AssertionResult::AssertionResult(const AssertionResult& other)    : success_(other.success_),      message_(other.message_.get() != NULL ?               new ::std::string(*other.message_) :               static_cast< ::std::string*>(NULL)) {}void AssertionResult::swap(AssertionResult& other) {  using std::swap;  swap(success_, other.success_);  swap(message_, other.message_);}AssertionResult AssertionResult::operator!() const {  AssertionResult negation(!success_);  if (message_.get() != NULL)    negation << *message_;  return negation;}