trompeloeil

Trompeloeil is a modern, open-source mocking framework for C++ used to facilitate unit testing by simulating dependencies and verifying interactions with them. It is designed to help tests focus on behavior by ensuring that the code under test communicates with its collaborators in the expected way.

Implemented as a header-only library, trompeloeil is designed to be easy to drop into existing projects and work with common testing frameworks such as Google Test and Catch2. The library emphasizes a lightweight integration model and aims to minimize external dependencies beyond the C++ standard library.

The framework provides a domain-specific language based on C++ templates and operator overloading to declare expectations describing which calls are allowed, with what arguments, in what order, and what they should return or do. This approach yields expressive, type-safe test specifications that are checked at runtime.

Mock targets typically include interfaces or classes with virtual functions; trompeloeil provides mechanisms to declare mocks, set up expectations for member functions and free functions, and verify call counts, argument matching, and call order. The framework supports configuring return values, actions, and side effects to simulate realistic behavior.

Additional features include argument matchers for flexible comparisons, support for sequencing and strict versus lenient expectations, and detailed failure messages when expectations are not met. Trompeloeil is intended to be portable across platforms and compilers supporting C++11 and later.

Development and licensing: trompeloeil is hosted on GitHub as an open-source project and is distributed under a permissive license, reflecting ongoing community maintenance and contribution.