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258 lines
5.8 KiB
Markdown
258 lines
5.8 KiB
Markdown
---
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description: 为 C++ 强制执行 TDD 工作流程。先编写 GoogleTest 测试，然后实现。使用 gcov/lcov 验证覆盖率。
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---
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# C++ TDD 命令
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此命令使用 GoogleTest/GoogleMock 与 CMake/CTest，为 C++ 代码强制执行测试驱动开发方法。
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## 此命令的作用
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1. **定义接口**：首先搭建类/函数签名
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2. **编写测试**：创建全面的 GoogleTest 测试用例（RED 阶段）
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3. **运行测试**：验证测试因正确原因失败
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4. **实现代码**：编写最少代码以通过测试（GREEN 阶段）
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5. **重构**：在保持测试通过的同时改进代码
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6. **检查覆盖率**：确保覆盖率在 80% 以上
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## 何时使用
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在以下情况使用 `/cpp-test`：
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* 实现新的 C++ 函数或类时
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* 为现有代码增加测试覆盖率时
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* 修复错误时（先编写失败的测试）
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* 构建关键业务逻辑时
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* 学习 C++ 中的 TDD 工作流时
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## TDD 循环
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```
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RED → 编写失败的 GoogleTest 测试
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GREEN → 实现最小化代码以通过测试
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REFACTOR → 改进代码，测试保持通过
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REPEAT → 下一个测试用例
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```
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## 示例会话
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````
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User: /cpp-test I need a function to validate email addresses
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Agent:
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# TDD Session: Email Validator
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## Step 1: Define Interface
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```cpp
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// validator/email.hpp
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#pragma once
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#include <string>
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#include <expected>
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enum class EmailError {
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Empty,
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InvalidFormat
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};
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std::expected<void, EmailError> validate_email(const std::string& email);
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```
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## Step 2: Write Tests (RED)
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```cpp
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// validator/email_test.cpp
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#include <gtest/gtest.h>
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#include "email.hpp"
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TEST(ValidateEmail, AcceptsSimpleEmail) {
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auto result = validate_email("user@example.com");
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EXPECT_TRUE(result.has_value());
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}
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TEST(ValidateEmail, AcceptsSubdomain) {
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EXPECT_TRUE(validate_email("user@mail.example.com").has_value());
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}
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TEST(ValidateEmail, AcceptsPlus) {
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EXPECT_TRUE(validate_email("user+tag@example.com").has_value());
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}
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TEST(ValidateEmail, RejectsEmpty) {
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auto result = validate_email("");
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ASSERT_FALSE(result.has_value());
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EXPECT_EQ(result.error(), EmailError::Empty);
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}
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TEST(ValidateEmail, RejectsNoAtSign) {
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EXPECT_FALSE(validate_email("userexample.com").has_value());
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}
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TEST(ValidateEmail, RejectsNoDomain) {
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EXPECT_FALSE(validate_email("user@").has_value());
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}
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TEST(ValidateEmail, RejectsNoLocalPart) {
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EXPECT_FALSE(validate_email("@example.com").has_value());
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}
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```
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## Step 3: Run Tests - Verify FAIL
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```bash
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$ cmake --build build && ctest --test-dir build --output-on-failure
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1/1 Test #1: email_validator_test .....***Failed
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--- undefined reference to `validate_email`
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FAIL
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```
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✓ Tests fail as expected (unimplemented).
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## Step 4: Implement Minimal Code (GREEN)
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```cpp
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// validator/email.cpp
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#include "email.hpp"
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#include <regex>
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std::expected<void, EmailError> validate_email(const std::string& email) {
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if (email.empty()) {
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return std::unexpected(EmailError::Empty);
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}
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static const std::regex pattern(R"([a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,})");
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if (!std::regex_match(email, pattern)) {
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return std::unexpected(EmailError::InvalidFormat);
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}
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return {};
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}
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```
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## Step 5: Run Tests - Verify PASS
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```bash
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$ cmake --build build && ctest --test-dir build --output-on-failure
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1/1 Test #1: email_validator_test ..... Passed 0.01 sec
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100% tests passed.
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```
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✓ All tests passing!
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## Step 6: Check Coverage
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```bash
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$ cmake -DCMAKE_CXX_FLAGS="--coverage" -B build && cmake --build build
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$ ctest --test-dir build
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$ lcov --capture --directory build --output-file coverage.info
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$ lcov --list coverage.info
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validator/email.cpp | 100%
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```
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✓ Coverage: 100%
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## TDD Complete!
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````
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## 测试模式
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### 基础测试
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```cpp
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TEST(SuiteName, TestName) {
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EXPECT_EQ(add(2, 3), 5);
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EXPECT_NE(result, nullptr);
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EXPECT_TRUE(is_valid);
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EXPECT_THROW(func(), std::invalid_argument);
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}
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```
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### 测试夹具
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```cpp
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class DatabaseTest : public ::testing::Test {
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protected:
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void SetUp() override { db_ = create_test_db(); }
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void TearDown() override { db_.reset(); }
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std::unique_ptr<Database> db_;
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};
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TEST_F(DatabaseTest, InsertsRecord) {
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db_->insert("key", "value");
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EXPECT_EQ(db_->get("key"), "value");
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}
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```
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### 参数化测试
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```cpp
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class PrimeTest : public ::testing::TestWithParam<std::pair<int, bool>> {};
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TEST_P(PrimeTest, ChecksPrimality) {
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auto [input, expected] = GetParam();
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EXPECT_EQ(is_prime(input), expected);
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}
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INSTANTIATE_TEST_SUITE_P(Primes, PrimeTest, ::testing::Values(
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std::make_pair(2, true),
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std::make_pair(4, false),
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std::make_pair(7, true)
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));
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```
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## 覆盖率命令
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```bash
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# Build with coverage
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cmake -DCMAKE_CXX_FLAGS="--coverage" -DCMAKE_EXE_LINKER_FLAGS="--coverage" -B build
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# Run tests
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cmake --build build && ctest --test-dir build
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# Generate coverage report
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lcov --capture --directory build --output-file coverage.info
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lcov --remove coverage.info '/usr/*' --output-file coverage.info
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genhtml coverage.info --output-directory coverage_html
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```
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## 覆盖率目标
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| 代码类型 | 目标 |
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|-----------|--------|
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| 关键业务逻辑 | 100% |
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| 公共 API | 90%+ |
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| 通用代码 | 80%+ |
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| 生成的代码 | 排除 |
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## TDD 最佳实践
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**应做：**
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* 先编写测试，再进行任何实现
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* 每次更改后运行测试
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* 在适当时使用 `EXPECT_*`（继续）而非 `ASSERT_*`（停止）
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* 测试行为，而非实现细节
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* 包含边界情况（空值、null、最大值、边界条件）
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**不应做：**
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* 在编写测试之前实现代码
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* 跳过 RED 阶段
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* 直接测试私有方法（通过公共 API 进行测试）
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* 在测试中使用 `sleep`
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* 忽略不稳定的测试
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## 相关命令
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* `/cpp-build` - 修复构建错误
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* `/cpp-review` - 在实现后审查代码
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* `/verify` - 运行完整的验证循环
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## 相关
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* 技能：`skills/cpp-testing/`
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* 技能：`skills/tdd-workflow/`
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