## About me * Canadian * Work at LSEG * Secretary of WG21 * Facilitator of Winnipeg C++ Developers * Licensed professional engineer * I like twisty puzzles  <!-- .element style="position:absolute; height:75%; right:0; top:12%;"-->

## Overview * Compile-time testing design decisions * My compile-time-first unit testing library `k3tchup` * "Regular" checks in `k3tchup` * "Stateful" checks in `k3tchup` * Questions at any time!

Compile-time testing design decisions

## Compile-time testing design decisions * "Out-of-source" vs "in-source" * When to report the errors * Test runner * Early exit mechanism

My compile-time-first unit testing library

## My unit testing library `k3tchup` * https://github.com/k3DW/k3tchup * C++20 library, decoupled from parsing library `tok3n` * Cross-platform (MSVC, Clang, GCC) * API inspired by GoogleTest * Functionality inspired by Snitch * Prioritizes compile-time testing * All errors are reported at run-time * Still a work in progress...

## `k3tchup` "regular" checks * Basic usage * Reusability for compile-time * Keeping the full trace * Dependent checks

Something still missing...

Compile-time testing design decisions

Ability to decide compile-time vs run-time for a whole function

k3tchup "stateful" checks

## `k3tchup` "stateful" checks * New overload of `ASSERT_THAT` and `EXPECT_THAT` * Convenience macros `ASSERT` and `EXPECT` * A whole new type of test * Accumulating errors at compile-time * The "constexpr two-step" * Merging the compile-time and run-time errors

Conclusion

## Expand your toolbox * Many specialized tools, but they may come in handy

## Test your code! * If you claim that your code runs at compile-time... * ...test it at compile-time * Your future self and your users will thank you

## `constexpr` code is vast and complex * But we can rein it in with compile-time testing * We can more rigorously test for correct program behaviour * Catch ill-formed programs early

## `k3tchup` makes it easy * Straight-line code for compile-time conditions * Equivalent to how you would do for run-time code * Entire tests can be run at compile-time and run-time * Scalable and ergonomic compile-time testing

Compile-time testing design decisions

Compile-time testing techniques

## `k3tchup` upcoming work * Refining the identifier choices (e.g. `TEST_CONSTEXPR`) * Integrating C++26 reflection * Tests for whether an expression _can_ run at compile-time * ...and more!

## `k3tchup` is a work in progress * Follow along at [https://github.com/k3DW/k3tchup](https://github.com/k3DW/k3tchup) * Please come talk to me about `constexpr` testing