Important

We're excited you're checking out Hegel! Hegel is in beta, and we'd love for you to try it and report any feedback.

As part of our beta, we may make breaking changes if it makes Hegel a better property-based testing library. If that instability bothers you, please check back in a few months for a stable release!

See https://hegel.dev/compatibility for more details.

Hegel for C++

• Documentation
• Website

Hegel is a property-based testing library for C++. Hegel is based on Hypothesis, using the Hegel protocol.

Installation

Hegel requires C++20.

To install with CMake, add this to your CMakeLists.txt (CMake 3.14+ required):

include(FetchContent)
FetchContent_Declare(
    hegel
    GIT_REPOSITORY https://github.com/hegeldev/hegel-cpp.git
    GIT_TAG v0.3.5
)
FetchContent_MakeAvailable(hegel)

target_link_libraries(your_target PRIVATE hegel)

Hegel will use uv to install the required hegel-core server component. If uv is already on your path, it will use that, otherwise it will download a private copy of it to ~/.cache/hegel and not put it on your path. See https://hegel.dev/reference/installation for details.

Quickstart

Here's a quick example of how to write a Hegel test:

#include <hegel/hegel.h>
#include <algorithm>
#include <stdexcept>
#include <vector>

namespace gs = hegel::generators;

std::vector<int> my_sort(std::vector<int> ls) {
    std::sort(ls.begin(), ls.end());
    ls.erase(std::unique(ls.begin(), ls.end()), ls.end());
    return ls;
}

int main() {
    hegel::test([](hegel::TestCase& tc) {
        auto vec1 = tc.draw(gs::vectors(gs::integers<int>()));
        auto vec2 = my_sort(vec1);
        std::sort(vec1.begin(), vec1.end());
        if (vec1 != vec2) {
            throw std::runtime_error("sort mismatch");
        }
    });

    return 0;
}

This test will fail! Hegel will produce a minimal failing test case for us:

Generated: [0,0]
libc++abi: terminating due to uncaught exception of type std::runtime_error:
Hegel test failed: sort mismatch

Hegel reports the minimal example showing that our sort is incorrectly dropping duplicates.