cpp-testinglisted

# C++ Testing (Agent Skill) Agent-focused testing workflow for modern C++ (C++17/20) using GoogleTest/GoogleMock with CMake/CTest. ## When to Use - Writing new C++ tests or fixing existing tests - Designing unit/integration test coverage for C++ components - Adding test coverage, CI gating, or regression protection - Configuring CMake/CTest workflows for consistent execution - Investigating test failures or flaky behavior - Enabling sanitizers for memory/race diagnostics ### When NOT to Use - Implementing new product features without test changes - Large-scale refactors unrelated to test coverage or failures - Performance tuning without test regressions to validate - Non-C++ projects or non-test tasks ## Core Concepts - **TDD loop**: red → green → refactor (tests first, minimal fix, then cleanups). - **Isolation**: prefer dependency injection and fakes over global state. - **Test layout**: `tests/unit`, `tests/integration`, `tests/testdata`. - **Mocks vs fakes**: mock for interactions, fake for stateful behavior. - **CTest discovery**: use `gtest_discover_tests()` for stable test discovery. - **CI signal**: run subset first, then full suite with `--output-on-failure`. ## TDD Workflow Follow the RED → GREEN → REFACTOR loop: 1. **RED**: write a failing test that captures the new behavior 2. **GREEN**: implement the smallest change to pass 3. **REFACTOR**: clean up while tests stay green ```cpp // tests/add_test.cpp #include <gtest/gtest.h> int Add(int a, int b); //