# Catch2 — Modern C++ Test Framework with Natural Expressions

> Catch2 is a header-only C++ testing framework known for its expressive assertion syntax and zero-config setup.

## Install

Save in your project root:

# Catch2 — Modern C++ Test Framework with Natural Expressions

## Quick Use
```bash
# Single-header install (v2) or CMake FetchContent (v3)
include(FetchContent)
FetchContent_Declare(Catch2 GIT_REPOSITORY https://github.com/catchorg/Catch2.git GIT_TAG v3.7.1)
FetchContent_MakeAvailable(Catch2)

# Link
target_link_libraries(my_tests PRIVATE Catch2::Catch2WithMain)

# Run
./my_tests --success
```

## Introduction
Catch2 is a C++ test framework that favors natural, readable test expressions over macro-heavy assertion APIs. It requires no external dependencies and integrates into any build system. Version 3 moved from a single header to a proper library while keeping the same expressive syntax.

## What Catch2 Does
- Lets you write assertions as plain C++ expressions: `REQUIRE(x == 42)`
- Supports BDD-style `SCENARIO` / `GIVEN` / `WHEN` / `THEN` sections
- Generates test cases from template parameters and data generators
- Provides built-in micro-benchmarking with `BENCHMARK` blocks
- Outputs results in JUnit XML, TAP, or compact console formats

## Architecture Overview
Catch2 v3 ships as a static library built with CMake. Test cases register themselves via static constructors into a global registry. The runner walks the registry, executing each section as an independent path through the test function. Generators produce lazy value sequences that expand into separate sub-cases at runtime, keeping memory use constant regardless of data set size.

## Self-Hosting & Configuration
- Install via CMake FetchContent, vcpkg, Conan, or your system package manager
- Use `--reporter junit` for CI-compatible XML output
- Tag tests with `[unit]`, `[integration]` etc. and filter with `--tags`
- Set `CATCH_CONFIG_FAST_COMPILE` to reduce compile times on large suites
- Integrate with CTest using the `catch_discover_tests()` CMake helper

## Key Features
- Natural expression assertions decompose both sides on failure automatically
- Section-based tests replace fixtures with scoped setup/teardown blocks
- Data generators (`GENERATE`) create parameterized tests inline
- Tag-based filtering lets you run subsets without recompiling
- Built-in benchmarking produces min/mean/max timing statistics

## Comparison with Similar Tools
- **GoogleTest** — more enterprise features and Google Mock integration; Catch2 has simpler setup and friendlier syntax
- **doctest** — even faster compile times; Catch2 offers richer generators and BDD sections
- **Boost.Test** — deep Boost ecosystem integration; Catch2 is standalone with fewer dependencies
- **CppUnit** — traditional xUnit style; Catch2 provides more expressive assertions
- **Criterion** — C-focused with parallel runners; Catch2 is C++-native with richer feature set

## FAQ
**Q: Should I use Catch2 v2 or v3?**
A: Version 3 is the actively maintained branch. It replaces the single header with a library for faster compiles.

**Q: Can Catch2 run tests in parallel?**
A: Catch2 does not parallelize internally. Use CTest or a CI matrix to run test binaries concurrently.

**Q: How do I integrate Catch2 with Bazel?**
A: Use `rules_foreign_cc` to build Catch2 with CMake inside Bazel, or vendor the built library as a precompiled dependency.

**Q: Does Catch2 support mocking?**
A: Catch2 has no built-in mocking. Pair it with trompeloeil, FakeIt, or any C++ mocking library.

## Sources
- https://github.com/catchorg/Catch2
- https://catch2.readthedocs.io/

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Source: https://tokrepo.com/en/workflows/c57a008a-4277-11f1-9bc6-00163e2b0d79
Author: AI Open Source