gtest-assertion-result.h

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// The Google C++ Testing and Mocking Framework (Google Test)
//
// This file implements the AssertionResult type.

// IWYU pragma: private, include "gtest/gtest.h"
// IWYU pragma: friend gtest/.*
// IWYU pragma: friend gmock/.*

#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_ASSERTION_RESULT_H_
#define GOOGLETEST_INCLUDE_GTEST_GTEST_ASSERTION_RESULT_H_

#include <memory>
#include <ostream>
#include <string>
#include <type_traits>

#include "gtest/gtest-message.h"
#include "gtest/internal/gtest-port.h"

GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251                                   \
/* class A needs to have dll-interface to be used by clients of class B */)

namespace testing {

// A class for indicating whether an assertion was successful.  When
// the assertion wasn't successful, the AssertionResult object
// remembers a non-empty message that describes how it failed.
//
// To create an instance of this class, use one of the factory functions
// (AssertionSuccess() and AssertionFailure()).
//
// This class is useful for two purposes:
//   1. Defining predicate functions to be used with Boolean test assertions
//      EXPECT_TRUE/EXPECT_FALSE and their ASSERT_ counterparts
//   2. Defining predicate-format functions to be
//      used with predicate assertions (ASSERT_PRED_FORMAT*, etc).
//
// For example, if you define IsEven predicate:
//
//   testing::AssertionResult IsEven(int n) {
//     if ((n % 2) == 0)
//       return testing::AssertionSuccess();
//     else
//       return testing::AssertionFailure() << n << " is odd";
//   }
//
// Then the failed expectation EXPECT_TRUE(IsEven(Fib(5)))
// will print the message
//
//   Value of: IsEven(Fib(5))
//     Actual: false (5 is odd)
//   Expected: true
//
// instead of a more opaque
//
//   Value of: IsEven(Fib(5))
//     Actual: false
//   Expected: true
//
// in case IsEven is a simple Boolean predicate.
//
// If you expect your predicate to be reused and want to support informative
// messages in EXPECT_FALSE and ASSERT_FALSE (negative assertions show up
// about half as often as positive ones in our tests), supply messages for
// both success and failure cases:
//
//   testing::AssertionResult IsEven(int n) {
//     if ((n % 2) == 0)
//       return testing::AssertionSuccess() << n << " is even";
//     else
//       return testing::AssertionFailure() << n << " is odd";
//   }
//
// Then a statement EXPECT_FALSE(IsEven(Fib(6))) will print
//
//   Value of: IsEven(Fib(6))
//     Actual: true (8 is even)
//   Expected: false
//
// NB: Predicates that support negative Boolean assertions have reduced
// performance in positive ones so be careful not to use them in tests
// that have lots (tens of thousands) of positive Boolean assertions.
//
// To use this class with EXPECT_PRED_FORMAT assertions such as:
//
//   // Verifies that Foo() returns an even number.
//   EXPECT_PRED_FORMAT1(IsEven, Foo());
//
// you need to define:
//
//   testing::AssertionResult IsEven(const char* expr, int n) {
//     if ((n % 2) == 0)
//       return testing::AssertionSuccess();
//     else
//       return testing::AssertionFailure()
//         << "Expected: " << expr << " is even\n  Actual: it's " << n;
//   }
//
// If Foo() returns 5, you will see the following message:
//
//   Expected: Foo() is even
//     Actual: it's 5

class GTEST_API_ AssertionResult {
 public:
  // Copy constructor.
  // Used in EXPECT_TRUE/FALSE(assertion_result).
  AssertionResult(const AssertionResult& other);

// C4800 is a level 3 warning in Visual Studio 2015 and earlier.
// This warning is not emitted in Visual Studio 2017.
// This warning is off by default starting in Visual Studio 2019 but can be
// enabled with command-line options.
#if defined(_MSC_VER) && (_MSC_VER < 1910 || _MSC_VER >= 1920)
  GTEST_DISABLE_MSC_WARNINGS_PUSH_(4800 /* forcing value to bool */)
#endif

  // Used in the EXPECT_TRUE/FALSE(bool_expression).
  //
  // T must be contextually convertible to bool.
  //
  // The second parameter prevents this overload from being considered if
  // the argument is implicitly convertible to AssertionResult. In that case
  // we want AssertionResult's copy constructor to be used.
  template <typename T>
  explicit AssertionResult(
      const T& success,
      typename std::enable_if<
          !std::is_convertible<T, AssertionResult>::value>::type*
      /*enabler*/
      = nullptr)
      : success_(success) {}

#if defined(_MSC_VER) && (_MSC_VER < 1910 || _MSC_VER >= 1920)
  GTEST_DISABLE_MSC_WARNINGS_POP_()
#endif

  // Assignment operator.
  AssertionResult& operator=(AssertionResult other) {
    swap(other);
    return *this;
  }

  // Returns true if and only if the assertion succeeded.
  operator bool() const { return success_; }  // NOLINT

  // Returns the assertion's negation. Used with EXPECT/ASSERT_FALSE.
  AssertionResult operator!() const;

  // Returns the text streamed into this AssertionResult. Test assertions
  // use it when they fail (i.e., the predicate's outcome doesn't match the
  // assertion's expectation). When nothing has been streamed into the
  // object, returns an empty string.
  const char* message() const {
    return message_ != nullptr ? message_->c_str() : "";
  }
  // Deprecated; please use message() instead.
  const char* failure_message() const { return message(); }

  // Streams a custom failure message into this object.
  template <typename T>
  AssertionResult& operator<<(const T& value) {
    AppendMessage(Message() << value);
    return *this;
  }

  // Allows streaming basic output manipulators such as endl or flush into
  // this object.
  AssertionResult& operator<<(
      ::std::ostream& (*basic_manipulator)(::std::ostream& stream)) {
    AppendMessage(Message() << basic_manipulator);
    return *this;
  }

 private:
  // Appends the contents of message to message_.
  void AppendMessage(const Message& a_message) {
    if (message_ == nullptr) message_ = ::std::make_unique<::std::string>();
    message_->append(a_message.GetString().c_str());
  }

  // Swap the contents of this AssertionResult with other.
  void swap(AssertionResult& other);

  // Stores result of the assertion predicate.
  bool success_;
  // Stores the message describing the condition in case the expectation
  // construct is not satisfied with the predicate's outcome.
  // Referenced via a pointer to avoid taking too much stack frame space
  // with test assertions.
  std::unique_ptr< ::std::string> message_;
};

// Makes a successful assertion result.
GTEST_API_ AssertionResult AssertionSuccess();

// Makes a failed assertion result.
GTEST_API_ AssertionResult AssertionFailure();

// Makes a failed assertion result with the given failure message.
// Deprecated; use AssertionFailure() << msg.
GTEST_API_ AssertionResult AssertionFailure(const Message& msg);

}  // namespace testing

GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4251

#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_ASSERTION_RESULT_H_