为模板类创建 gtest 值参数化测试

Question

我有一个类型的模板类

<size_t N>
class Line {
   ...
};

我怎样才能为这个类的几个实例创建一个测试？例如 Line<1>, Line<2>, ...

我检查了文档，有：

• 值参数化测试，用于运行时值

• 类型参数化测试，允许您在编译时更改类型名称。

但是，我没有找到任何可以在编译时更改值的内容。

Answer 1

Googletest 没有现成的解决方案，可以根据需要在模板上为一组非类型模板参数生成测试。

假设使用 C++11 或更高版本，您可以利用std::integral_constant<T,N> 来创建一个类，该类唯一地表示您希望测试覆盖的std::size_t 参数范围中的每一个，并 用作构造 a和关联s的代理。像这样：NLine<N>std::integral_constant<std::size_t,N>NTYPED_TEST_CASETYPED_TEST

Line用于说明的玩具类：

行.h

#ifndef LINE_H
#define LINE_H
#include <cstddef>

template <std::size_t N>
class Line {
public:
    static constexpr std::size_t capacity() {
        return N;
    }
    explicit Line(std::size_t n)
    : _length{n < N ? n : N}{};

    std::size_t length() const {
        return _length;
    }

private:
    std::size_t _length = 0;

};

#endif

Googletest 测试运行程序：

line_test.cpp

#include <gtest/gtest.h>
#include <type_traits>
#include "line.h"

template <typename T>
class line_tester : public ::testing::Test{};

using test_types = ::testing::Types<
    std::integral_constant<std::size_t,2>,
    std::integral_constant<std::size_t,3>, 
    std::integral_constant<std::size_t,5>>;

TYPED_TEST_CASE(line_tester, test_types);

TYPED_TEST(line_tester, get_capacity) {
    static constexpr std::size_t n = TypeParam::value;
    ASSERT_EQ(n,Line<n>::capacity());
}

TYPED_TEST(line_tester, set_length_preserved) {
    Line<TypeParam::value> line{1};
    ASSERT_EQ(line.length(),1);
}

TYPED_TEST(line_tester, set_length_trunctated) {
    static constexpr std::size_t n = TypeParam::value;
    Line<n> line{999};
    ASSERT_EQ(line.length(),Line<n>::capacity());
}

int main(int argc, char **argv) {
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}

运行如下：

$ ./line_tester 
[==========] Running 9 tests from 3 test cases.
[----------] Global test environment set-up.
[----------] 3 tests from line_tester/0, where TypeParam = std::integral_constant<unsigned long, 2ul>
[ RUN      ] line_tester/0.get_capacity
[       OK ] line_tester/0.get_capacity (0 ms)
[ RUN      ] line_tester/0.set_length_preserved
[       OK ] line_tester/0.set_length_preserved (0 ms)
[ RUN      ] line_tester/0.set_length_trunctated
[       OK ] line_tester/0.set_length_trunctated (0 ms)
[----------] 3 tests from line_tester/0 (1 ms total)

[----------] 3 tests from line_tester/1, where TypeParam = std::integral_constant<unsigned long, 3ul>
[ RUN      ] line_tester/1.get_capacity
[       OK ] line_tester/1.get_capacity (0 ms)
[ RUN      ] line_tester/1.set_length_preserved
[       OK ] line_tester/1.set_length_preserved (0 ms)
[ RUN      ] line_tester/1.set_length_trunctated
[       OK ] line_tester/1.set_length_trunctated (0 ms)
[----------] 3 tests from line_tester/1 (0 ms total)

[----------] 3 tests from line_tester/2, where TypeParam = std::integral_constant<unsigned long, 5ul>
[ RUN      ] line_tester/2.get_capacity
[       OK ] line_tester/2.get_capacity (0 ms)
[ RUN      ] line_tester/2.set_length_preserved
[       OK ] line_tester/2.set_length_preserved (0 ms)
[ RUN      ] line_tester/2.set_length_trunctated
[       OK ] line_tester/2.set_length_trunctated (0 ms)
[----------] 3 tests from line_tester/2 (0 ms total)

[----------] Global test environment tear-down
[==========] 9 tests from 3 test cases ran. (1 ms total)
[  PASSED  ] 9 tests.