Here’s what we do in MSVC’s STL: constexpr bool test_is_even() { assert(is_even(0)); assert(!is_even(1)); // … more test coverage

Here’s what we do in MSVC’s STL: constexpr bool test_is_even() { assert(is_even(0)); assert(!is_even(1)); // … more test coverage return true; } int main() { test_is_even(); // runtime coverage static_assert(test_is_even()); // compile-time coverage This lets us run all test cases at both runtime and compiletime. (The static_assert performs constant evaluation, and if an assert within test_is_even would fail, it won’t be a constant expression.)